JR'S Free Thought Pages
Logical Argumentation & the Art of Critical Thought
Footnotes are at the end of the paper
Before you begin, and if you have not already done so, you may want to read the page titled Commonplace Nonsense
"No man who is indifferent to argument and to evidence can claim to be concerned for truth." - Antony Flew (1975), Thinking About Thinking, p. 14.
"The challenge to think better is a challenge to our integrity." - Antony Flew, Ibid, p. 113.
Logic, according to the Oxford dictionary, is the science of reasoning, proof, thinking, or inference. It describes the relation between language and the world, in its most systematic outline. Logic was first given formal expression by Aristotle, the famous Greek philosopher, almost 2500 years ago. In his well-known treatises, he described the way we try to discover the truth - observing the world, selecting impressions, making inferences and generalizing. In this process Aristotle identified two forms of reasoning: induction and deduction. Both forms, he realized, are subject to error. Our observations may be incorrect or insufficient, and our conclusions may be faulty because they have violated the rules governing the relationships between statements.
Logic allows us to analyze a piece of reasoning and determine whether it is correct or not (valid or invalid). It is an attempt to provide a theory of what makes an argument good. Two factors can make an argument bad: if the assumptions it starts from are ambiguous, unclear, or simply false, or if it reasons from these assumptions in the wrong way. For example, one of the most common errors in reasoning is the introduction of an irrelevant issue, one that has little or no direct bearing on the development of the argument.
When people make statements, they may offer evidence to support them or they may not. A statement that is supported by evidence is the conclusion of the argument, and logic provides the tools for the analysis of arguments. Logical analysis is concerned with the relationship between a conclusion and the evidence given to support it and with methods for distinguishing those arguments that are logically sound from those which are not.
Of course, one does not need to study logic in order to reason correctly; nevertheless, a little basic knowledge of logic is often helpful when constructing or analyzing an argument. In ordinary usage, the term "argument" signifies a dispute but in logic it does not have that connotation. As we use the term, an argument can be given to justify a conclusion, whether or not anyone openly disagrees. However, intelligent disputation - as opposed to the sort of thing that consists of loud shouting and name-calling - does involve argument in the logical sense. You may have seen the Monty Python skit in which a man enters a room and asks, “Is this the right room for an argument?” The occupant answers, “I already told you once”, to which the first man replies, “No, you didn’t”, and is told, “Yes, I did”. They then begin shouting at one another, hurling the same charges back and forth again and again. This is not what logicians have in mind when they talk about “arguments”.
Hence, for one who is interested in seeking an intelligent, reasonable resolution to a disagreement, it is an occasion for providing evidence and appealing to the rules of logic. Arguments are often designed to convince, and this is one of their important and legitimate functions; however, logic is not concerned with the persuasive power of arguments. Arguments that are logically incorrect often do convince, while logically impeccable arguments often fail to persuade. A person may be persuaded by an abominable argument; just as he may remain unconvinced by considerations which he certainly would accept if he were more rational, or more honest, or both. Roughly speaking, then, an argument is a group of statements standing in relation to its supporting evidence. More precisely, an argument consists of one statement that is the conclusion and one or more supporting statements of supporting evidence. The statements of evidence are called premises.
Note that no claim is being made here about whether logic is universally applicable. The matter is very much open for debate. This paper merely attempts to explain how to use logic, given that you have already decided that logic is the right tool for the job. Certainly there is an important place in life for passion, compassion, humour and commitment and it is important to understand that rationality and emotion are not logical opposites or mutually exclusive entities. But these emotions should not be allowed to inhibit one's objectivity, judgement and ability to get at the truth.
Propositions (or statements) are the building blocks of a logical argument. A proposition is a statement that is either true or false; for example, "It is raining" or "Today is Tuesday". Propositions may be either asserted (said to be true) or denied (said to be false). Note that this is a technical meaning of "deny", not the everyday meaning. The proposition is the meaning of the statement, not the particular arrangement of words used to express it. So "God exists" and "There exists a God" both express the same proposition. To be able to say correctly that a statement is true, one must be able to: (1) know what the statement means (i.e., its propositional content). However, as Immanuel Kant has pointed out over 200 years ago, knowing what X means or having a concept of X does not allow one to necessarily conclude that X exists. For example, we have a concept of a unicorn, but we cannot infer from this that unicorns exist, (2) know how to verify the statement and (3) have good reasons and evidence for believing the statement - psychological, emotional or practical reasons (i.e., motives) for believing a statement are irrelevant to the question of whether or not the statement is true.
An argument is, to quote the Monty Python sketch, "a connected series of statements to establish a definite proposition". An argument consists of three stages.
First of all, the propositions which are necessary for the argument to continue are stated. These statements, as has been previously mentioned, are called the premises of the argument. They are the evidence or reasons for accepting the argument and its conclusions. Premises (or assertions) are often indicated by phrases such as "because", "since", "obviously" and so on. (The phrase "obviously" is often viewed with suspicion, as it can be used to intimidate others into accepting suspicious premises. If something doesn't seem obvious to you, don't be afraid to question it. You can always say, "Oh, yes, you're right, it is obvious" when you've heard the explanation.)
Next, the premises are used to derive further propositions by a process known as inference. In inference, one proposition is arrived at on the basis of one or more other propositions already accepted. There are various forms of valid inference. The propositions arrived at by inference may then be used in further inference. Inference is often denoted by phrases such as "implies that" or "therefore".
Finally, we arrive at the conclusion of the argument ‑ the proposition that is affirmed on the basis of the premises and inference. Conclusions are often indicated by phrases such as "therefore", "hence", "thus", "consequently", "it follows that", "we conclude", and so on. The conclusion is often stated as the final stage of inference. For example:
Every event has a cause (premise)
The universe has a beginning (premise)
All beginnings involve an event (premise)
This implies that the beginning of the universe involved an event (inference)
Therefore the universe has a cause (inference and conclusion)
Note that the conclusion of one argument might be a premise in another argument. A proposition can only be called a premise or a conclusion with respect to a particular argument; the terms do not make sense in isolation. Sometimes an argument will not follow the order given above; for example, the conclusions might be stated first and the premises stated afterwards in support of the conclusion. This is perfectly valid, if sometimes a little confusing.
Recognizing an argument is much harder than recognizing premises or conclusions. Many people shower their writing with assertions without ever producing anything which one might reasonably describe as an argument. Some statements look like arguments, but are not. For example:
"If the Bible is accurate, Jesus must either have been insane, a pernicious liar or the Son of God."
This is not an argument - it is a conditional statement. It does not assert the premises that are necessary to support what appears to be its conclusion. (It also suffers from a number of other logical flaws, but we'll come to those later.)
"God created you; therefore do your duty to God."
The phrase "do your duty to God" is not a proposition, since it is neither true nor false (It is a command). Therefore it is not a conclusion, and the sentence is not an argument.
Finally, causal relationships are important. Consider a statement of the form "A because B". Here, event B is a cause that produces effect A. Causes are, as it were, the moving forces of the world. We refer to them in various ways: we may say that one event leads to another, produces it, brings it about, makes it happen, forces it, stops it, prevents it, stems it, increases it - the list goes on. No two or three terms can be depended on to cue causal arguments. You will have to judge whether a causal claim is involved, and if so, if the argument supporting the claim is a sound one. Errors in reasoning about cause-effect relationships are extremely common and can at times result in horrendous mistakes, made not only by members of the general populace, but by professional people as well. A recent case involved a discharged U.S. Marine who received an $850,000 severance cheque from the U.S. government as the result of a computer error. The ex-marine proceeded to spend over $400,000 of the money, and later argued that prior to receiving the cheque he had been praying to God that his "luck" would change - and his prayers were answered. Needless to say, the government was not impressed by this causal argument. A systematic account of causation and causal reasoning, however, is far beyond the scope of this paper. It should be pointed out that causation and causal inference are still hotly debated topics in philosophical and scientific circles. If we are interested in establishing the truth of A, and B is offered as evidence, the statement is an argument. If we're trying to explain or justify the truth of B when the truth of B is already taken for granted, then it is not an argument, but an explanation.
"There must be something wrong with the engine of my car, because it will not start." ‑‑ this is an argument.
"My car will not start because there is something wrong with the engine." ‑‑ this is an explanation.
Generally, an explanation is an attempt to indicate how or why an event occurred. Where explanation is appropriate, there is usually no question whether or not the event did occur. That much is either known to be true or accepted as true. The explanation is an attempt to make the event more intelligible or understandable. An argument, on the other hand, is an attempt to demonstrate that something is true. We employ arguments precisely when doubt exists about a statements truth. The difference between an argument and an explanation is clear enough in the abstract, but it can be very difficult to decide, in concrete instances, whether a passage is an argument or an explanation. In the example above, some confusion may result from the use of the word "because" - a word that often precedes a premise in an argument. Also, it is not possible for the same set of propositions to function simultaneously as an argument and an explanation.
There are two traditional types of argument, deductive and inductive. A deductive argument is one that provides conclusive proof of its conclusions ‑‑ that is, an argument where if the premises are true, the conclusion must also be true. A deductive argument is either valid or invalid. A valid argument is defined as one whereby if the premises are true, then the conclusion is true (Do not confuse "validity" with "truth" - validity refers only to the logical structure of an argument whereas truth is a property of propositions). Validity is a hypothetical or conditional characteristic; it assures us that the conclusion of the argument is true if the premises are true. An argument may be said to be valid in virtue of its form. For example, if (1) If everything is caused, then no one acts freely, and (2) Everything is caused, are both true, then it must also be true that (3) No one acts freely. We can represent the preceding argument in the following valid form, known as Modus Ponens.
If P, then Q Modus Ponens
Some other valid argument forms are:
Modus Tollens Disjunctive Syllogism
If P, then Q Either P or Q
Not Q Not P
Therefore, Not P Therefore, Q.
Hypothetical Syllogism Constructive Dilemma
If P, then Q Either P or Q
If Q, then R If P, then R
---------------- If Q, then S
Therefore, If P then R ---------------------
Therefore, Either R or S
De Morgan’s Laws
(1) Not (P or Q) = Not P and Not Q: If a disjunction is false, then all its disjuncts are false and vice versa.
(2) Not (P and Q) = Not P or Not Q : If a conjunction is false, then at least one of its conjuncts is false, and vice versa.
Reductio ad Absurdum ("Indirect" proof)
To prove: P
Assume: Not P
From the assumption, derive an implication: Q
Show: Q is false (contradictory, inconsistent, silly, absurd)
The idea of a reductio ad absurdum is to establish a conclusion by refuting its opposite, and it is an especially attractive tactic when what you are attempting to refute is your opponent's position in order to prove your own.
An invalid argument form is called a formal fallacy. In such cases, the premises do not logically entail the conclusion - this error is referred to as a non sequitur, which means literally “it does not follow”. It is an unfortunate human tendency to believe much more than is actually warranted from the premises. Many informal fallacies fall under the rubric of irrelevancy, including appeals to authority and the ad hominem fallacy. These will be discussed later. Two common formal fallacies are:
Affirming the Consequent Denying the Antecedent
If P, then Q If P, then Q
Q Not P
Therefore, P Therefore, Not Q
An inductive argument is an argument relevant to one kind of assertion only; namely to empirical or factual claims and one in which the premises provide some evidence for the truth of the conclusion. Deductive reason is at the heart of Mathematical reasoning, whereas inductive reasoning is the logical underpinning for the Scientific Method. Inductive arguments are not valid or invalid; however, we can talk about whether they are better or worse than other arguments, and about how probable their premises are. An inductive argument is one whose conclusion is claimed to be more or less probable, but not certain. Inductive arguments can grow better or worse as new evidence comes in. There are degrees of strength or support. They are "justified" when they have enough good evidence to support their conclusion. Consider the following arguments, one deductive, and the other inductive:
Deductive: Every mammal has a heart
All whales are mammals
Therefore, every whale has a heart.
Inductive: Every whale that has been observed so far has a heart.
Therefore, every whale has a heart.
Consider the following two inductive arguments:
(1) Three hundred and fifty persons observed in a sample of 500 smokers have cardiovascular disease.
Therefore, smoking causes cardiovascular disease.
(2) All smokers have cardiovascular disease or will develop it during their lifetime.
Therefore, smoking causes cardiovascular disease.
The difference between arguments (1) and (2) is that of quantity or scope. The conclusion in each case is causative and the premise in (2) could quite easily have been a conclusion of the premise in (1). The conclusion reached in each of the arguments, which may or may not be warranted, could be a possible hypothesis or conjecture. A more cautious inductive inference from the premises might be: "Smoking is a factor in the cause of cardiovascular disease in some persons."
The deductive argument is designed to make explicit the content of the premises; the inductive argument is designed to extend the range of our knowledge. There are forms of argument in ordinary languages that are neither deductive nor inductive. However, we will concentrate for the moment on deductive arguments, as they are often viewed as the most rigorous and convincing. It is important to note that the fact a deductive argument is valid does not imply that its conclusion holds. This is because of the slightly counter‑intuitive nature of implication, which we must now consider more carefully. Obviously a valid argument can consist of true propositions. However, an argument may be entirely valid even if it contains only false propositions. For example:
All insects have wings (premise)
Frogs are insects (premise)
Therefore frogs have wings (conclusion)
Here, the conclusion is not true because the argument's premises are false. If the argument's premises were true, however, the conclusion would be true. The argument is thus entirely valid. In a subtler manner, we can reach a true conclusion from one or more false premises, as in:
An elephant is bigger than a mouse (premise)
A mouse is bigger than a horse (premise)
Therefore, an elephant is bigger than a horse (conclusion)
On the other hand, an argument may have true premises and true conclusions and still be invalid. Consider:
The earth has one moon.
Snow is white.
Therefore, crows are black.
However, the one thing we cannot do is reach a false conclusion through valid inference from true premises. We can therefore draw up a "truth table" for implication.
The symbol "=>" denotes implication; "A" is the premise, "B" the conclusion. "T" and "F" represent true and false respectively.
Premise Conclusion Inference
A B A=>B
F F T If the premises are false and the inference
F T T valid, the conclusion can be true or false.
T F F If the premises are true and the conclusion false, the inference must be invalid.
T T T If the premises are true and the inference valid, the conclusion must be true.
A sound argument is a valid argument whose premises are true. A sound argument therefore arrives at a true conclusion. Be careful not to confuse valid arguments with sound arguments.
An argument is sound if (i) its logic is good and (ii) the information in it is correct. A deductive argument is sound when it is both valid and contains only true propositions. An inductive argument is sound when it is both justified and contains only true propositions.
But determining the soundness of arguments is not a simple matter, for three reasons.
First, before we can assess an argument we must determine its precise meaning. It would be convenient if the meaning of arguments were always clear, but unfortunately this is often not so. An argument may be unclear because the meaning of one or more of its statements is unclear, or because the nature of the connection that is being asserted between the premises and conclusion is unclear. This means we have to learn how to interpret statements and arguments in a way that makes their meaning as clear as possible. The skills needed for this task are interpretive skills.
Second, determining the truth or falsity of statements is often a difficult task. Even when we are sure we know precisely what a statement means we may be unsure about its truth, and may even be unsure how to go about determining whether it is true or false. As we shall see, there are several different types of statements, and each type has its own method for determining truth and falsity. The skills needed for this task are verification skills.
Third, assessing arguments is complex because there are several different types of inferences, and each type requires a different kind of assessment. It is necessary to learn how to recognize these different types of inferences and to become familiar with these different methods of assessment. For this purpose reasoning skills are needed.
These three types of skills ‑ interpretive skills, verification skills, and reasoning skills ‑ constitute what are usually referred to as critical thinking skills. Developing a mastery of them is important for several practical reasons.
First, we are inundated with information of all sorts, but this information is useless unless we know how to use it in our thinking to draw out its implications and consequences. Much of it is incomplete and one-sided in ways that are often not apparent, and if we are not on our guard we may be misled.
Second, we are constantly presented with arguments designed to get us to accept some conclusion that we would otherwise not accept. Politicians, preachers, advertisers, editorial writers, and special‑interest groups of all sorts spend a great deal of time, thought, and money attempting to persuade us to believe the things they want us to believe, and it is important to be on guard against arguments that fail to meet the appropriate logical criteria. This is partly a matter of our own self‑interest, for when others seek to make us believe things that are in their interest it is possible, or even likely, that our interests are not being well served.
Third, mastering critical thinking skills is also a matter of intellectual self‑respect. We all have the capacity to learn how to distinguish good arguments from bad ones and to work out for ourselves what we ought and ought not to believe, and it diminishes us as persons if we let others do our thinking for us. If we are not prepared to think for ourselves, and to make the effort to learn how do this well, we will always be in danger of becoming slaves to the ideas and values of others and to our own ignorance.
And finally, critical thinking skills can make it easier for us to persuade others to change their beliefs. Many beliefs are based more on emotion than on reason, although those holding them usually believe they are based on reason. In fact, it is rare to find a person, even a complete bigot, who does not believe that his or her beliefs have a rational basis. Critical thinking skills can often be effective in dislodging such beliefs, and persuading others to change their views.
This last point raises a number of moral questions. Like any skill, critical thinking skills can be used for good or ill. There are many ways in which they can be abused. They can be used to make a bad argument look much stronger than it really is, and to make an opponent's position look much weaker than it really is. They can be used to make us look wise, and to make others look foolish. They can be used to avoid having to respond to legitimate criticisms, and to persuade others to change their beliefs for inadequate reasons. Every day we find ourselves in situations in which we could use our critical thinking skills for such purposes, and sometimes we may be tempted to do so. Yielding to the temptation, however, is dishonest and hypocritical.
Consider these two valid arguments that have diametrically opposed conclusions, one of which must be unsound. Hence one or more of the premises of one of the arguments must be false. Which premises would you challenge?
(1) The world exhibits conclusive evidence of design.
(2) If the world exhibits conclusive evidence of design, then the world has a designer who is God.
(3) Therefore, God exists.
(1a) If God exists; there is an all-powerful, all-knowing, and perfectly good being who created the world.
(2a) If there is an all-powerful, all-knowing, and perfectly good being who created the world, then the world is free of evil.
(3a) The world is not free of evil.
(4a) Therefore, God does not exist.
To delve further into the structure of logical arguments would require a lengthy discussion of linguistics and philosophy. It is simpler and probably more useful to summarize the major pitfalls to be avoided when constructing an argument. These pitfalls are known as fallacies. In everyday English the term "fallacy" is used to refer to mistaken beliefs as well as to the faulty reasoning that leads to those beliefs. This is fair enough, but in logic the term is generally used to refer to a form of technically incorrect argument, especially if the argument appears valid or convincing. So for the purposes of this discussion, we define a fallacy as an argument which appears to be correct, but which can be seen to be incorrect when examined more closely or an argument that should not persuade a rational person to accept its conclusion. Inductive fallacies result from the wrong use of evidence: for example, the arguer leaps to a conclusion on the basis of an insufficient sample, ignoring evidence that might have altered her conclusion. Deductive fallacies, on the other hand, result from a failure to follow the rules of logic in a series of statements. Here the arguer neglects to make a clear connection between the various parts of her argument.
Below is a list of some common fallacies, and also some rhetorical devices often used in debate. Fallacies are difficult to classify, first, because there are literally dozens of systems for classifying, and second, because under any system there is always a good deal of overlap. Therefore, the following list is not intended to be exhaustive.
ARGUMENTUM AD BACULUM (APPEAL TO FORCE)
The Appeal to Force is committed when the arguer resorts to force or the threat of force in order to try and push the acceptance of a conclusion. It is often used by politicians, and can be summarized as "might makes right". The force threatened need not be a direct threat from the arguer. For example:
"... Thus there is ample proof of the truth of the Bible. All those who refuse to accept that truth will burn in Hell."
ARGUMENTUM AD HOMINEM
Argumentum ad hominem is literally "argument directed at the man". The abusive variety of Argumentum ad Hominem occurs when, instead of trying to disprove the truth of an assertion or the evidence for the argument, the arguer attacks the person's personality, character, circumstances, motives, qualifications, etc. This is invalid because the truth of an assertion does not depend upon the goodness of those asserting it. For example:
"Atheism is an evil philosophy. It is practised by Communists and dictators."
"Eric Hoffer knows nothing about philosophy. He's a longshoreman."
Sometimes in a court of law doubt is cast upon the testimony of a witness by showing, for example, that he is a known perjurer. This is a valid way of reducing the credibility of the testimony given by the witness, and not argumentum ad hominem; however, it does not demonstrate that the witness's testimony is false. To conclude otherwise is to fall victim of the Argumentum ad Ignorantiam (see elsewhere in this list).
The circumstantial form of Argumentum ad Hominem is committed when a person argues that his opponent ought to accept the truth of an assertion because of the opponent's particular circumstances. For example:
"It is perfectly acceptable to kill animals for food. How can you argue otherwise when you're quite happy to wear leather shoes?"
This is an abusive charge of inconsistency, used as an excuse for dismissing the opponent's argument. This fallacy can also be used as a means of rejecting a conclusion. For example:
"Of course you would argue that positive discrimination is a bad thing. You're white."
This particular form of Argumentum ad Hominem, when one alleges that one's adversary is rationalizing a conclusion formed from selfish interests is known as poisoning the well. "Poisoning the well" is also construed as an attempt to shift attention from the merits of the argument - the validity of the reasoning, the truth of the claims - to the source or origin of the argument. For example, the mere fact that Stalin or Hitler believed something does not show that the belief is false or immoral; just because some scoundrel believes the world is round, that is no reason for you to believe it is flat.
ARGUMENTUM AD IGNORANTIAM
Argumentum ad ignorantiam means "argument from ignorance" or "appeal to ignorance". This fallacy occurs whenever it is argued that something must exist or be true simply because it has not been proved false. Or, conversely, when it is argued that something must be false because it has not been proved true. The absence of evidence establishes nothing; what we don't know cannot be evidence for (or against) anything! Our ignorance is no reason for believing anything, except perhaps that we ought to try to undertake an appropriate investigation in order to reduce our ignorance and replace it with reliable information. (Note that this is not the same as assuming that something is false until it has been proved true, a basic scientific principle.) Examples:
"Of course God exists and the Bible is true. Nobody can prove otherwise."
"Of course ESP and other psychic phenomena do not exist. Nobody has shown any proof that they are real."
Part of the temptation to believe that proof by ignorance is real proof may stem from the fact that is some courts of law a defendant is presumed innocent until proven guilty. In other words, lack of evidence against someone is taken as proof, for the purposes of the court, that they did not commit the crime. However, as many cases of guilty people being freed because of a lack of evidence show, this in not really a proof, of innocence, but merely a practical, if imprecise, way of protecting innocent people from wrongful conviction.
Also, in scientific investigation if it is known that an event would produce certain evidence of its having occurred, the absence of such evidence can validly be used to infer that the event did not occur. For example:
"A flood as described in the Bible would require an enormous volume of water to be present on the earth. The earth does not have a tenth as much water, even if we count that which is frozen into ice at the poles. Therefore no such flood occurred."
In science, we can validly assume from lack of evidence that something has not occurred. However, we cannot conclude with certainty that it has not occurred.
ARGUMENTUM AD MISERICORDIAM
This is the Appeal to Pity, also known as Special Pleading. The fallacy is committed when the arguer appeals to pity or sympathy or "moralizes" for the sake of getting a conclusion accepted. It amounts to inconsistency in the sense that one finds reasons where his advantage lies but refuses to apply the same principle to others. For example:
"If I don't get an "A" in this course, I won't be on the honour roll."
"I really worked hard in this course, therefore I should get a pass."
"I'm 38 years old and out here busting my butt in this heat and you call the ball out. It was on the line!" (Jimmy Connors at the 1992 U.S. Open)
"I did not murder my mother and father with an axe. Please don't find me guilty; I'm suffering enough through being an orphan."
This fallacy is closely related to "wishful thinking" or "rationalization". It amounts to ignoring or refusing to look for evidence that we do not want to face or which might refute our position. Like the ostrich with his head in the sand, we ignore the facts. For example:
"He will recover from cancer, because he is a good man and good men deserve to live a lot longer than he has lived."
A subtler version of special pleading is the one closely associated with Voltaire’s famous statement: “Superstition is someone else’s religion.” Voltaire’s point is that most people who belong to one religion or another believe that their religion is the TRUE religion and all others are false. Their God, their Sacred Book and their Prophet are the genuine material whereas all others are bogus and mindless superstition. This fallacy is a form of self-righteousness and hypocrisy in the sense that if these same people applied the same rules of evidence to their own faith that they applied in rejecting the faith of others, they would have to reject their own as well.
ARGUMENTUM AD POPULUM
This is known as Appealing to the Gallery, or Appealing to the People. To commit this fallacy is to attempt to win acceptance of an assertion by appealing to the majority, to what is popular - mob appeal. It often amounts to arguing in order to arouse an emotional, popular acceptance of an idea without resorting to a logical justification of the idea. An appeal is made to such things as biases, prejudices, feelings, enthusiasms, and attitudes of the multitude rather than to rational support of the idea. This is the strategy of many demagogues - remember Mark Antony's speech in Julius Caesar? For example:
"Pornography must be banned. It is violence against women."
"The Bible must be true. Millions of people know that it is. Are you trying to tell them that they are all mistaken fools?"
Contemporary America seems prone to this fallacy and was referred to as early as 150 years ago by Alexis de Toqueville as the “tyranny of the majority” in his book Democracy in America. John Stuart Mill and Ralph Waldo Emerson were two other Eighteenth Century intellectuals who also pointed this out. That the majority of people believe a proposition does not imply its truth. Most people, for example, once believed the earth was flat. When one becomes aware of the pervasiveness of psychics, televangelists, self-help gurus and pseudo-scientific nonsense on television this state of affairs is not getting any better.
Bertrand Russell once wrote “The fact that an opinion is widely held is no evidence whatever that it is not utterly absurd; indeed, in view of the silliness of the majority of mankind, a wide-spread belief is more likely to be foolish than sensible.” (Marriage and Morals)
ARGUMENTUM AD NUMERUM
This fallacy is closely related to the argumentum ad populum. It consists of asserting that the more people who support or believe a proposition, the more likely it is that the proposition is correct. Or, an unreliable method of reasoning which treats majority opinion by voting as a source of truth or a reliable guide for action on every question (The Democratic Fallacy) On many issues one must appeal to an expert or recognized authority. Those who want to put every issue to a vote are often shirking their responsibility to make a decision. Democracy is of value only in certain contexts - what is desired is an informed majority, not just a majority.
"It must be a good book - it's on the best seller list."
"Since most people believe in God and all cultures have had some concept of God, he must exist."
“The pilot of the airliner polled the passengers and the majority concluded that an emergency landing was warranted, hence an emergency landing is the most rational course of action.”
ARGUMENTUM AD VERECUNDIAM
The Appeal to Authority uses the admiration of the famous to try and win support for an assertion. For example:
"Isaac Newton was a genius and he believed in God."
"Albert Einstein was a genius and he did not believe in God."
"We must obey the Ten Commandments - they are the will of God."
"Domino's Pizza is great - Wayne Gretzky says so."
"Abortion / Homosexuality is wrong because the Bible prohibits it."
This line of argument is not always completely bogus; for example, reference to an admitted authority in a particular field may be relevant to a discussion of that subject. For example, we can distinguish quite clearly between:
"Stephen Hawking has concluded that black holes give off radiation" and "John Searle has concluded that it is impossible to build an intelligent computer". Hawking is a physicist, and so we can reasonably expect his opinions on black hole radiation to be informed. Searle is a respected philosopher of mind, but it is arguable whether he is well‑qualified to speak on the subject of machine intelligence.
Arguing that something is true because it has practical effects upon people: it consoles them or makes them happier, easier to deal with, more moral, loyal, and stable. The prudential argument presented by Blaise Pascal in his famous "Wager" is tainted in this way. Pascal argued that one should believe in the proposition "God exists" because it is prudent to do so and has consolatory and salutary effects on the believer. Another similar example:
"One should believe in immortality because without such a concept people have nothing to live for. There would be no meaning or purpose in life and everyone would be immoral."
THE FALLACY OF ACCIDENT
The Fallacy of Accident is committed when a general rule is applied to a particular case whose "accidental" circumstances mean that the rule is inapplicable. It is the error made when one goes from the general to the specific. For example:
"Christians generally dislike atheists. You are a Christian, so you must dislike atheists."
Moralists and legalists who try to decide every moral and legal question by mechanically applying general rules often commit this fallacy. In the realm of ethics, philosophers refer to this error as casuistry. For example:
"Thou shalt not bear false witness [lie], therefore you should tell the rapist where your sister is hiding." or
"One should not break promises. Therefore I should not break the promise to play tennis with Ralph in order to save this drowning child."
The general requirement that promises should not be broken has a tacit qualification like "all things being equal" or "in the absence of an overriding obligation". When there is a drowning child, all things are not equal, because there is an overriding obligation to save the child. During the Nuremberg Trials, the oft-heard excuse of Nazi and Gestapo members in their treatment of Jewish people that they were only following orders of their superiors is a case in point. Although one has an obligation to obey one's superiors, the obligation is overridden by the obligation to respect the minimal human rights of other people.
CONVERSE ACCIDENT / HASTY GENERALIZATION
This fallacy is the reverse of the fallacy of accident. It occurs when one forms a general rule by examining only a few specific cases that are not representative of all possible cases. This fallacy is loosely related to "slanting" - the finding or looking only for evidence that supports a pre-determined (or a priori) conclusion. Rationalizations, the finding of bad reasons or evidence that support what one already believes or intends to believe anyway, are similar self-serving biases. For example:
"Jim Bakker, Peter Popoff and Jimmy Swaggart are insincere Christians. Therefore, all Christians are insincere."
"Both Socrates and Jesus Christ, two famous martyrs, accepted slavery and we know that slavery is wrong. Therefore, all martyrs are immoral."
SWEEPING GENERALIZATION / DICTO SIMPLICITER
A sweeping generalization occurs when a general rule is applied to a particular situation in which the features of that particular situation render the rule inapplicable. A sweeping generalization is the opposite of a hasty generalization. For example:
"I believe in the Golden Rule as an inherent duty to do unto others as I would have them do unto me. If I were unable to answer a question on an examination, I would want my neighbour to help me. So it is my duty to help the person sitting next to me who asked me to give her the answer to a question on this exam."
NON CAUSA PRO CAUSA / POST HOC ERGO PROPTER HOC
These are known as False Cause fallacies. The fallacy of Non Causa Pro Causa often occurs when one identifies something as the cause of an event but it has not actually been shown to be the cause. For example:
"I took an aspirin and prayed to God, and my headache disappeared. So God cured me of the headache."
The fallacy of Post Hoc Ergo Propter Hoc occurs when something is assumed to be the cause of an event merely because it happened before the event. For example:
"The Soviet Union collapsed after taking up atheism. Therefore we must avoid atheism for the same reasons."
Statistical relationships often have nothing to do with cause and effect. For example:
"Very few automobile accidents occur when driving over 150 km/h. Therefore, one should drive over 150 km/h."
"People with large feet are better at mathematics than people with small feet. Therefore, having big feet is a reliable measure of one's mathematical ability."
Many superstitious beliefs are based on the post hoc fallacy. Accidents are attributed to walking under a ladder, breaking a mirror or a black cat walking across one's path. Many athletes are superstitious in this way - they wear a particular item of clothing before a contest and attribute this to their winning. When people read their horoscopes, which tend to be very general and universally applicable, they only look for evidence that confirms the horoscope prediction and ignore evidence to the contrary. The horoscope then becomes a self-fulfilling prophecy - which is particularly the case when the person is already a believer in Astrology. It is extremely alarming how many people believe in Astrology in spite of the fact that numerous scientific studies have shown Astrology to be false! Astrology is a pre-scientific cosmology (over 2000 years old) that attempts to predict the future and people's psychological make-up and predispositions based on the movements of the planets!! Of course, the mass media, particularly the newspapers, are extremely irresponsible in their promotion of this bogus belief system.
CUM HOC ERGO PROPTER HOC
This fallacy is similar to post hoc ergo propter hoc. It asserts that because two events occur together, they must be causally related, and leaves no room for other factors that may be the cause(s) of the events. For example:
"Sunday causes Monday."
“Mozart had a spine and heart and was a great composer; I have a spine and heart so I’ll probably turn out to be a great composer.”
PETITIO PRINCIPII / BEGGING THE QUESTION
This fallacy occurs when the premises are at least as questionable as the conclusion reached. It amount to circuitous reasoning - a logical "spinning of the wheels". For example:
"Murder is immoral because it is wrongful killing."
"The wealthy should be taxed heavily because they have a lot of money."
"The Universe has a beginning. Everything that has a beginning has a beginner. Therefore, the Universe has a beginner called God."
"Aristocracy is the best form of government because the best form of government is one in which there is strong aristocratic leadership."
This type of reasoning is often found in what are described as "closed systems" of thought. Closed systems bring out the worst kind of intellectual dishonesty and self‑righteousness. Moreover, closed systems are both self-fulfilling and self-defeating. Seeking to explain everything, they explain nothing. When defending their views, people frequently try to make their statements and arguments safe by reducing them to what philosophers call tautologies: that is, to the sort of statements that are necessarily true because the person making the assertions have made them true by definition or defend them against challenges by appealing to the truth of the system itself. For example, consider the following dialogue:
True Believer: "Do you know why you refuse to accept the truth of our religion? Do you know what your problem is? It's pride - sinful pride. And pride, my friend, is the work of Satan."
Skeptic: "I do not believe in Satan."
True Believer: "I understand, but that disbelief is itself the work of Satan. Don't you see how manipulative Satan can be?"
CIRCULUS IN DEMONSTRANDO
This fallacy occurs when one assumes as a premise the conclusion which one wishes to reach. Often, the proposition will be rephrased so that the fallacy appears to be a valid argument. For example:
"Homosexuals must not be allowed to hold government office. Hence any government official who is revealed to be a homosexual will lose his job. Therefore homosexuals will do anything to hide their secret, and will be open to blackmail. Therefore homosexuals cannot be allowed to hold government office."
Note that the argument is entirely circular; the premise is the same as the conclusion. An argument like the above has actually been cited as the reason for the British Secret Services' official ban on homosexual employees.
Another example is the classic:
True Believer: "God exists!"
Skeptic: "How do you know that God exists?"
True Believer: "It says so right here in the Bible."
Skeptic: "How do you know that what the Bible says is true.”?
True Believer: "It's the word of God."
COMPLEX QUESTION / FALLACY OF INTERROGATION
This fallacy is the interrogative form of “begging the question”. The question asked depends on a premise that has not been addressed. Those door-to-door proselytising evangelists such as the Jehovah Witnesses are notorious in committing this fallacy when they ask the question:
“What do you think God has planned for the human race?”
The hidden premise here is “God exists” and is precluded by the above statement.
Another example is the classic loaded question:
"Have you stopped beating your wife?"
The question presupposes a definite answer to another question that has not even been asked or creates the impression that a prior question has already been answered. It begs the question because it attempts to force a respondent to grant an assumption that is itself in need of proof. Lawyers in cross‑examination often use this trick, when they ask questions like:
"Where did you hide the money you stole?"
Or, a teacher might pose this question to a suspected cheater:
"Did you cheat by copying from your neighbour or by smuggling in your notes?"
Similarly, politicians often ask loaded questions such as:
"What are your views on the token effort made by the government to deal with this monstrous national debt?"
"Was it stupidity or through deliberate dishonesty that the administration hopelessly botched our relations with Japan?"
Commonly called the Fallacy of Irrelevant Conclusion, it consists of claiming that an argument supports a particular conclusion when it is actually logically nothing to do with that conclusion. This fallacy is sometimes used to describe all fallacies of irrelevance.
For example, a Christian may begin by saying that he will argue that the teachings of Christianity are undoubtedly true. If he then argues at length that Christianity is of great help to many people, no matter how well he argues he will not have shown that Christian teachings are true.
Sadly, such fallacious arguments are often successful because they arouse emotions that cause others to view the supposed conclusion in a more favourable light.
EQUIVOCATION / AMBIGUITY
Equivocation occurs when a key word is used with two or more different meanings in the same argument. This fallacy is committed when words or phrases become unclear because of shifts in meaning from one premise to another. For example:
"Since an elephant is an animal, a small elephant must be a small animal."
"The end of a thing is its perfection. Death is the end of life. Therefore, death is the perfection of life."
One common violation is the use of a word in one premise in a metaphorical sense and in another premise in a literal sense. For example, someone may refer to the “miracles of science” which is obviously used metaphorically whereas another person may refer to the “miracle of Christ” which is using the word “miracle” in the literal sense.
"The fact that there are laws of nature such as gravitation and motion shows that God exists. For the existence of a law implies the existence of a lawgiver, and God is the Supreme lawgiver in the Universe. So, far from disproving the existence of God, science, in detecting the laws of nature, actually proves that God exists." The ambiguous word here is "law". This word has two quite different meanings. It may mean "an observed regularity in nature"; it may also mean "a prescription or imperative set forth by a duly constituted authority." The equivocation of the word "law" in the above argument is blatantly obvious, and hence the argument is fallacious.
One of the most blatant misuses of ambiguous language involves use of the word "natural". Advertisers and other sophists associate what is "natural" with the "good" and what is "unnatural with the "bad". For example, "Smoking is good because cigarettes contain natural ingredients". The word nature has a built-in ambiguity that can lead to serious misunderstandings. When something is said to be "natural" or in conformity with natural law" or the "laws of nature", this may mean either (1) that it is in conformity with the descriptive laws of nature, or (2) that it is not artificial, that man has not imposed his will or his devices upon events or conditions as they exist or would have existed without such interference. If we accept the premises that "What is natural is good" and "What is unnatural is bad" then we are lead to absurdities such as: "Tornadoes, hurricanes, earthquakes, and deadly viruses are natural, therefore they are good" and "Antibiotics, vaccinations, artificial heart valves and hip joints are unnatural, therefore they are bad". The word "faith" is ambiguous in the sense that one may have a rational faith or an irrational faith. For example it may be rational to state "I have faith that Sam will show up for this important meeting" because their is good reason for the belief (i.e., there is prior evidence to trust or have confidence in Sam's reliability) as opposed to statements such as "I have faith that my prayers will be answered" which is based on little or no empirical evidence.
Closely related to equivocation is the attempt to invoke stipulative definitions, which are the result of a conscious and explicit decision as to how a word or phrase is to be used, rather than on the analysis of how that word is commonly understood. Psychologists are especially guilty of this manoeuvre. The meaning of the word “intelligent” has been distorted in this way by adding a variety of non-cognitive criteria to what it means to be called “intelligent”, criteria that are at variance to our ordinary usage of the word. This ploy often results in a definition so broad that it’s meaning is reduced to a vacuity. For example, if, for the purposes of enhancing self-esteem or some other ulterior motive, everyone is now defined to be intelligent, then the word has no special meaning.
Amphiboly occurs when the premises used in an argument are ambiguous because of careless or ungrammatical phrasing. For example:
"We Dispense with Accuracy." (Druggist's sign)
"Old cow pasture." (Sign on an empty field) - For old cows only?
Accent is another form of fallacy through shifting meaning. In this case, altering which parts of a statement are emphasized changes the meaning. For example, consider:
"We should not speak ILL of our friends" and "We should not speak ill of our FRIENDS" and "We should not speak ill of OUR friends" and "WE should not speak ill of our friends".
FALLACIES OF COMPOSITION
One fallacy of composition is to conclude that a property shared by the parts of something must apply to the whole. For example:
"Every thing in the Universe has a cause. Therefore the Universe as a whole has a cause."
"The bicycle is made entirely of low mass components, and is therefore very lightweight."
The other fallacy of composition is to conclude that a property of a number of individual items is shared by a collection of those items. For example:
"A car uses less petrol and causes less pollution than a bus. Therefore cars are less environmentally damaging than buses."
"A line of five NHL all-stars is the best line in hockey because each of the five players is the best at his position."
FALLACY OF DIVISION
The fallacy of division is the opposite of the fallacy of composition. Like its opposite, it exists in two varieties. The first is to assume that a property of some thing must apply to its parts. For example:
"You are studying at a rich college. Therefore you must be rich."
The other is to assume that each item shares a property of a collection of items. For example:
"Ants can destroy a tree. Therefore this ant can destroy a tree."
"The Toronto Stock Exchange composite index was up 100 points today. Therefore my stock International Widgets is up today."
"The Vancouver Canucks played well and had a great victory last night. Therefore Pavel Bure played well last night."
THE GAMBLER'S FALLACY
Arguing that, for example, that since a penny has fallen tails ten times in a row that it is more likely that it will fall heads on the eleventh. A batter in baseball has not had a hit in the last twenty times at bat and therefore he is due for a hit. The gambler's fallacy (or Monte Carlo fallacy) rejects the principle in probability theory that each event is independent of its previous occurrence. It is the failure to see that what are called “independent events” is equally probable and that a coin, for example, has no memory and its future "behaviour" is not affected by past occurrences. The error of assuming that since something has happened less frequently in the past, then it has an increased probability of happening in the future. The serious lack of understanding of the fundamentals of probability theory among the general public is appalling - and it is no more obvious than at the long line-ups where retailers sell lottery tickets.
THE NATURALISTIC FALLACY (IS/OUGHT OR FACT/VALUE DICHOTOMY)
An error in reasoning (although not considered so by some philosophers) which deduces conclusions about what ought to be from premises that state only what is the case. From a description of facts it is impossible to assert moral strictures or arrive at ethical convictions. The source of this error can be found in David Hume's Treatise of Human Nature and is often referred to as "Hume's Fork". The label "Naturalistic Fallacy" is apt, since many specimens centre upon what is natural. For instance, because a certain kind of conduct is natural to most of us, because that it is something which most of us are naturally inclined, therefore it must be at least warranted if not positively obligatory. Arguments against homosexuality often take this form.
This fallacy is sometimes referred to as the fallacy of moralism. It involves the unwarranted assumption that simply because something is the case, it ought to be the case or that because something is not the case that it ought not to be the case. The fallacy is often invoked in attempts to establish that a particular behaviour or conduct is right on the basis of its being displayed by a large number of people or on the basis that it preserves the status quo (e.g., we have always done it that way). If most people do not do something, which does not make it wrong; if most people do it, that does not make it right. For example, most people are right-handed; does this mean that being left-handed is wrong. The fallacy of moralism can be detected in some of the arguments that have been advanced in favour of moral relativism - the theory that what we believe to be good and right can be understood only in the context of our own society or culture. This viewpoint drew support from the findings of pioneer sociologists and anthropologists that the ideals of one society may be diametrically opposed to those of another society. It is the belief that ethical standards are culturally determined. For example, polygamy and infanticide are right in some societies but deemed wrong in our society. Slavery was justified in ancient Rome and in the Confederate States of the United States in the early Nineteenth Century because it was accepted by those cultures. Does this also mean that modern day Sweden is no more ethical, rational or just that Nazi Germany or modern day Iraq? I would think not. Cultural and moral relativism espouse what philosophers know as a pragmatic theory of truth - what is true is what is practical or "whatever works" for that particular person or culture. The crucial flaw of some arguments for ethical relativism is the assumption that "whatever a society or culture believes is good, is good for them." But it does not follow from the fact that different cultures have different institutions and beliefs that all beliefs or viewpoints are equally worthy, rational or correct and that there are no universal moral principles. Thus, a person who argues that it is pointless to apply moral principles to the behaviour of persons in other cultures - for the reason that people in these cultures do not observe those principles - commits the fallacy of moralism. This fallacy is loosely related to "wishful thinking" which occurs when one attempts to draw the conclusion that something is true from premises that express wishes, hopes, motives, desires or beliefs about right and wrong.
THE SLIPPERY SLOPE ARGUMENT
This argument states that should one event occur, it will set off a chain of events that ultimately will lead to other undesirable or harmful events. There is no proof made that the harmful events are caused by the first event. For example:
"If we legalize marijuana, then we would have to legalize crack and heroin and we'll have a nation full of drug‑addicts on welfare. Therefore we cannot legalize marijuana."
The fallacy here is in implying that the first step necessarily leads to the second, and so on down the slope to disaster, when in fact there is no necessary connection between the first step and the second at all. (Would gun registration lead to a police state? Well, it hasn't happened is Switzerland; not yet.) Sometimes the argument takes the form of claiming that a seemingly innocent or even attractive principle that is being applied in a given case (censorship of pornography, to avoid promoting sexual violence) requires one for consistency to apply the same principle in other cases with absurd and catastrophic results (censorship of everything in print, to avoid hurting people's feelings or banning baseball bats because some people have been killed by them).
"A IS BASED ON B" FALLACIES / "IS A TYPE OF" FALLACIES
These fallacies occur when one attempts to argue that things are in some way similar without actually specifying in what way they are similar. Examples:
"Isn't history based upon faith? If so, then isn't the Bible also a form of history?"
"Islam is based on faith, Christianity is based on faith, so isn't Islam a form of Christianity?"
"Cats are a form of animal based on carbon chemistry, dogs are a form of animal based on carbon chemistry, so aren't dogs a form of cat?"
AFFIRMATION OF THE CONSEQUENT
See page 4-5.
This fallacy is an argument of the form "A implies B, B is true, therefore A is true". To understand why it is a fallacy, examine the truth table for implication given earlier.
DENIAL OF THE ANTECEDENT
See page 4-5.
This fallacy is an argument of the form "A implies B, A is false, therefore B is false". Again, the truth table for implication makes it clear why this is a fallacy. Note that this fallacy is different from Non Causa Pro Causa; the latter has the form "A implies B, A is false, therefore B is false", where A does NOT in fact imply B at all. Here, the problem is not that the implication is invalid; rather it is that the falseness of A does not allow us to deduce anything about B.
CONVERTING A CONDITIONAL
This fallacy is an argument of the form "If A then B, therefore if B then A". (These last three fallacies are formal deductive fallacies.)
THE GENETIC FALLACY
Sometimes called the "reductive fallacy" or "nothing-but fallacy". (i) Arguing that the antecedents, source or origins of something must be the same as their fulfilment, (ii) Arguing that something is to be rejected because its origins and/or the person endorsing it are suspicious or (iii) Appraising or explaining something in terms of its origin, source or beginnings. It would be omitted by anyone who argued, presumably in the context of the abortion debate, that a foetus, even from the moment of conception, must really be, because it is going to become, a person. But the fallacy is usually exemplified in equations moving in the opposite direction from the actual or supposed antecedent to the developed whatever it may be. For example:
"The Declaration of Independence should be rejected because Thomas Jefferson was a slaveholder."
"The death penalty was used by the Spanish Inquisition. Therefore, we should reject the death penalty in our system of justice."
ARGUMENTUM AD ANTIQUITATEM
This is the fallacy of asserting that something is right or good simply because it is old, or because "that's the way it's always been." In other words, precedent is substituted for reasoning. For example:
"Let's stick to the tried-and-true methods" or "We like to do things by the book" or "If it ain't broke, why fix it?"
ARGUMENTUM AD NOVITATEM
This is the opposite of the argumentum ad antiquitatem; it is the fallacy of asserting that something is more correct simply because it is new or newer than something else.
ARGUMENTUM AD CRUMENAM
The fallacy of believing that money is a criterion of correctness; that those with more money are more likely to be right.
ARGUMENTUM AD LAZARUM
The fallacy of assuming that because someone is poor he or she is sounder or more virtuous than one who is wealthy. This fallacy is the opposite of the argumentum ad crumenam.
ARGUMENTUM AD NAUSEAM
This is the incorrect belief that an assertion is more likely to be true the more often it is heard. An "argumentum ad nauseam" is one that employs constant repetition in asserting something. The old adage "tell people something often enough and they end up believing it" has a certain element of truth to it. Advertisers are aware of this truism.
Also referred to as the "black and white" fallacy, bifurcation occurs when one presents a situation as having only two alternatives, an either-or polarity or false dilemma, when in fact other alternatives exist or can exist. This fallacy presents contraries as if they were contradictories. Two statements are said to be contraries when it is impossible for them both to be true but possible for them both to be false. Two statements are said to be contradictories, on the other hand, when it is impossible for them both to be true but also impossible for them both to be false (e.g., You are either dead or alive). Advertisers frequently use this device. For example:
"Either you go to college or forget about getting a job."
"One must either be married or be celibate."
"America: love it or leave it."
"If you know about BMW, you either own one or you want one."
PLURIUM INTERROGATIONUM / MANY QUESTIONS
This fallacy occurs when a questioner demands a simple answer to a complex question.
This fallacy is committed when irrelevant material is introduced to the issue being discussed, so that everyone's attention is diverted away from the points being made, towards a different conclusion. For example:
"You believe in abortion, yet you don't believe in the right-to-die with dignity bill before the legislature."
"I fail to see why hunting should be considered cruel when it gives tremendous pleasure to people and employment to many others."
REIFICATION / HYPOSTATIZATION
Reification occurs when an abstract concept is treated as a concrete thing. For example:
"The State can do no wrong" or "Science makes progress" or "Your soul goes to heaven when you die" or "This team has no spirit."
SHIFTING THE BURDEN OF PROOF
The burden of proof is always on the person making an assertion or proposition. Shifting the burden of proof, a special case of argumentum ad ignorantiam, is the fallacy of putting the burden of proof on the person who denies or questions the assertion being made. The source of the fallacy is the assumption that something is true unless proven otherwise. It is wise to heed Thomas Henry Huxley's famous quote: "Extraordinary claims require extraordinary evidence." This dictum is particularly applicable to claims of paranormal experiences such as ESP, telekinesis, precognition, reincarnation and near death experiences that have not stood up to scientific investigation and are inconsistent with our everyday sensory experiences.
The straw man fallacy is to misrepresent someone else's position so that it can be attacked more easily, then to knock down that misrepresented position, then to conclude that the original position has been demolished. Hence, when you misrepresent your opponent's position, attribute to that person a point of view with a set-up implausibility that you can easily demolish, and then proceed to argue against the set-up version as though it were your opponents; you commit the "straw man." It is a fallacy because it fails to deal with the actual arguments that have been made.
THE EXTENDED OR FALSE ANALOGY
The fallacy of false analogy is an argument involving the mistaken inference that because two or more things share the same superficial similarities, they will be alike in significant and relevant respects. By focusing on superficial similarities and ignoring important differences, fallacies of faulty analogy distort the facts. For example:
"Why should we sentimentalize over a few hundred thousand Native Americans who had their culture destroyed when our great civilization was being built? It may be that they suffered a few injustices, but after all, you can't make an omelette without breaking a few eggs."
"What is taught in public school should depend entirely on what students are interested in. After all, consuming knowledge is like consuming anything else in our society. The teacher is the seller, the student the buyer. Buyers determine what they want to buy, so students should determine what they want to learn."
Consider the following argument that confuses saving a demented person from killing himself with "saving one's soul". Evangelists often plead that a person accept Christianity for his own good in the same sense that one would do everything possible to save a madman from killing himself.
Evangelist: That man is a lunatic.
Skeptic: Why is that?
Evangelist: Because he won't accept Jesus Christ as his personal saviour.
Skeptic: But how do you know that a man who doesn't accept Jesus Christ as his personal saviour is a lunatic.
Evangelist: Because anyone who doesn't accept Jesus Christ as his personal saviour must be a lunatic.
Perhaps the most famous example of a false analogy is the "Design Argument" for the existence of God, first challenged by David Hume in his Dialogues Concerning Natural Religion. During the last 200 years, most philosophers have accepted the conclusion reached by Immanuel Kant in his Critique of Pure Reason, namely, that all rational attempts to prove God's existence have failed. The argument to design, which has highly contentious premises, can be formulated as follows:
Beautiful and well-built watches must have "makers": intelligent designers and builders.
The world is like a beautiful and well-built watch. _____________________________________________________________
Therefore, the world must have a "maker": an intelligent designer and builder called God.
In other words, since there are visible similarities between natural objects and those which have been designed by human beings - between the human eye and a camera, for instance - we can conclude that both must have been produced by a similar sort of intelligence. Perceivable similarities between two sorts of things are taken as a reliable indication that they have similar sorts of origin: in this case an intelligent designer. Because they eye is more sophisticated in “design” than the camera, using this argument from analogy, we can conclude that the designer of the eye was more intelligent and powerful than the designer of the camera. The conclusion is that this more intelligent and powerful designer is an entity called “God”. However, as many eminent philosophers have pointed out, the analogy between the eye and a camera are extremely weak. Although there are respects in which they are similar (they both have lenses), there are also numerous respects in which they differ (the eye is part of a living organism whereas the camera is part of a machine). Moreover, there is a highly plausible alternate explanation that is backed up by a massive volume of scientific evidence - Darwin’s theory of evolution and natural selection.
This is the famous "you too" fallacy. It occurs when an action is argued to be acceptable because the other party has performed it or that a person's views are inconsistent with what he previously believed and therefore (i) is not to be trusted and/or (ii) his views are to be rejected. Sometimes related to the fallacy of "two wrongs make a right" - a logical fallacy employed primarily in ethical arguments and appealing to very strong emotional and psychological factors. This is the argument that justifies a wrongful action or practice because it has become commonly accepted or is practised by many. For example:
"You're just being randomly abusive."
"So? You've been abusive too."
"Everyone cheats on their taxes, so I will too."
AUDIATUR ET ALTERA PARS
Often, people will argue from assumptions that they do not bother to state. The principle of Audiatur et Altera Pars is that all of the premises of an argument should be stated explicitly. It is not strictly a fallacy to fail to state all of one's assumptions; however, it is often viewed with suspicion.
As was stated earlier, if we're interested in establishing A, and B is offered as evidence, the statement "A because B" is an argument. If we're trying to establish the truth of B, then "A because B" is not an argument, it is an explanation.
The Ad Hoc fallacy is to give an after‑the‑fact explanation that does not apply to other situations. Often this ad hoc explanation will be dressed up to look like an argument. For example:
"I was healed from cancer."
"Praise the Lord, then. He is your healer."
"So, will He heal others who have cancer?"
"Ah, well, The ways of God are mysterious."
ARGUMENTUM AD LOGICAM
This is the "fallacy fallacy" of arguing that a proposition is false merely on the grounds that it has been presented as the conclusion of a fallacious argument. Remember always that fallacious arguments can arrive at true conclusions.
We frequently get trapped into passionate arguments about religion and politics which could be short-circuited by applying a criterion known as the principle of falsifiability - a rational standard formulated by the eminent philosopher of science, Karl Popper. The falsifiability principle tells us that a statement of fact (e.g., "Angels exists", "Astrology is true", "All people are greedy") is meaningful if, and only if, it can be disproved. In other words, when someone is arguing a case, he also has to tell you what would have to be the case to show that his assertion is false or what it would take to force him into an admission that he is wrong. What evidence would blow his position out of the water, or at the very least, weaken it? Because if nothing can possibly undermine his view; if nothing could be possibly said, facts or reasons, then he is simply making a dogmatic assertion - in short, he is preaching. The assertion becomes a matter of faith, not reason. Good scientific theories are always falsifiable. The law of gravitation, for example, would be falsified if what went up, did not come down and the statement "All crows are black" would be falsified if we observed a non-black crow.
An example of an argument that is flawed in this way is an argument for ethical egoism. The ethical egoist argues that all acts are selfishly motivated and that one's only duty is to promote one's own interests. The volunteer who helps out at the food bank, the boy who returns the lost wallet and the person who helps a stranger with her flat tire is acting out of a hidden self-interest and an attempt to make themselves feel good. Sympathy, compassion, and other acts of kindness or altruism are really self-serving and selfish - attempts to make us look and feel good. The next time you are confronted with such an argument, invoke Popper's falsifiability principle. When the ethical egoist insists that we all act only in our self-interest - not that everyone should be selfish, but that everyone is selfish - ask him what a non-selfish act would look like. If he tells you that it's impossible for anyone to act without selfish motives, then make it clear that he's including selfishness in the definition of the word "act." Not only does he have a depraved notion of morality but he also suffers from a serious deficiency in his use of the English language. Gilbert Ryle, the renowned Cambridge philosopher, explains this misuse of language in his 1954 book Dilemmas. Ryle uses the example of counterfeit currency - if one speaks of counterfeit currency, then there must be genuine currency. First, says Ryle "A country which has no coinage would offer no scope to counterfeiters. There would be nothing for them to manufacture or pass counterfeits of." On the other hand, if a person were to claim that a particular country had only counterfeit currency, there must be an answer to the question "counterfeits of what?" Ryle continues with another illustration, when he asks us to consider
...a judge, who has found all too many witnesses in the past inaccurate and dishonest... [he] may be right to expect today's testimonies to break down under examination; but he cannot declare that there are no such things as accuracy and sincerity in testifying. Even to consider whether this witness has been insincere or inaccurate involves considering what would be the honest or precise thing to say. Ice could not be thin if ice could not be thick. (Ryle, 1954, p. 95)
 Aristotle formulated three very basic laws which he felt formed the foundations of rational thought: (1) Identity - a thing is equal to itself; (2) The Law of Non-contradiction - no statement can be both true and false; and (3) The law of the Excluded Middle - any statement must be either true of false.
 Antony Flew, in Thinking About Thinking, calls this the "Subject/Motive shift" - a move from discussing rational grounds for the truth or falsity of some proposition to discussing the quite different question of what someone's motives or desires might be for asserting or denying the proposition. "When someone is said to have some reason for believing a certain proposition, we may need to ask: whether this reason is a ground for holding that the proposition is actually true; or whether it is a motive for persuading himself of it, irrespective of whether it is true or not. In the former case we can speak of a reason (ground), in the latter of a reason (motive)" (Flew , p. 58)
 If two events occur together regularly, then there is a correlation between the two, but not necessarily a causative relationship. If A and B occur together with regularity, a number of possible hypotheses may explain the correlation: A may be the cause of B, B may be the cause of A, another event C may be the cause of both A and B or there may be a coincidence between the occurrence of A and B.
 In philosophical discussions concerning causation, philosophers and scientists distinguish between necessary causal conditions and sufficient causal conditions. By a sufficient condition is meant an event or factor that suffices to bring about another event. "X is sufficient for Y" means "If X occurs, Y occurs." A burnt-out light bulb, for example, is a sufficient causal condition for a light not to go on. So is a broken switch, a burnt-out fuse or a power failure. The occurrence of any one of these is sufficient to cause the light's failure. A necessary condition is an event or factor whose absence prevents another from occurring. "X is a necessary condition for Y" means "If Y occurs, X must have occurred." So, for example, an unbroken electrical circuit is a necessary condition for a light to go on. If the light does go on, the electricity must be flowing through an unbroken circuit. And if this condition is absent - if the current is broken - then the light is prevented from going on. Many causes consist of a collection of factors where each one is causally necessary, and all together are jointly causally sufficient, to bring about the effect.
 Casuistry, in its pejorative sense, is construed as sophistical, equivocal, false or misleading reasoning or teaching about one's moral conduct, duties and principles. It involves dialectical skill in finding reasons for wriggling out of ethical principles when they become inconvenient, usually by misapplying a general ethical principle in a particular context.
 Antony Flew (1975) states that there is always the possibility that one may be mistaken and humility and "any forthright concern for truth demands an emphasis upon the possibilities of falsification." Anyone professing sincerity, concern for truth and intellectual integrity must "give due weight to reasonable and relevant objections". To fail to do so is "to show that you are more concerned to maintain that belief than really to know whether it or some other is, after all, true." (p. 115)