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Mastering Logical Fallacies: The Definitive Guide to Flawless Rhetoric and Bulletproof Logic


Have you ever felt like you’re in a discussion where the other person isn’t following the rules of logic? Have you ever felt like you knew things were off but you weren’t sure exactly why? I’ve felt that way, and that’s why when the book Mastering Logical Fallacies: The Definitive Guide to Flawless Rhetoric and Bulletproof Logic came across my email, I knew I wanted to read it.

Discussions and Arguments

Before I dive into the logical fallacies and how they are categorized, it’s necessary to stop and understand the context under which these rules apply. These rules apply to a structured disagreement. It’s about how people who are interested in improving understanding and coming to a common understanding.

Consider the story of Bill, an expert kickboxer, who frequently wins regional championships. In a dark alley he’s confronted with someone who demands his money. Knowing his prowess in the ring, he starts to defend himself. The criminal who demanded his money pulls out his gun and shoots him. The rules of logical arguments are applicable to places where the rules of discussion are well-defined. However, these aren’t necessarily the skills to bring out when having a disagreement with your spouse. (If you decide that this is the right answer you might consult The Science of Trust.)

While the rules of logic may rule a court of law, they’re very little good in the court of public opinion. While they’re powerful tools for agreement, they may be rendered powerless in an argument with flared tempers. The rules presented in Mastering Logical Fallacies are the rules of ordered debate, not the rules for arguing with a sibling or for dealing with Internet trolls.

Discussions often hold to rules of decorum, even if they’re not explicitly defined. While they rarely elevate to the level of a dialogue (see Dialogue for more) they can sometimes descend past disagreement and fall into the pit of an argument. These rules are effective in a discussion and in a disagreement, but sometimes understanding only gets you so far when it comes to arguments.


I mentioned in my review of Switch and The Happiness Hypothesis – and several times since – that I love the model of the rider-elephant-path for describing the relationship between our rational self, our emotional self, and our environment. Kurt Lewin said that behavior is a function of both person and environment. In the rider-elephant-path model, the environment is the path. And what Lewin simplifies to the variable person are two related factors of the rider and the elephant.

While Mastering Logical Fallacies focuses in on the rider and how to make rational, logical arguments, there are many admissions that we’re not just rational creatures. There’s an acknowledgement that even though some emotional arguments aren’t rational they’re often quite effective. I find that arguments tend to be more emotional than rational. By knowing the rules of logical arguments you can – perhaps – avoid the degeneration into an emotional argument.

Rhetorical Techniques

Like a magician performing sleight of hand, sometimes the argument is less about the argument and more about what the opposing party can pull off while you’re not paying attention. Plays on emotion, instead of logic and reason, are popular ways to derail and discussion – particularly in politics or the court of public opinion.

A regular argument or debate, however, should be ruled by logic and not by emotion. Mastering Logical Fallacies is a toolbox to ensure that your arguments and responses follow the rules of logic.

Formal and Informal

The first distinction in the book is the difference between formal and informal fallacies. This major dividing line is between the arguments that are invalid by their structure, and those whose lack of validity is based on their content. Of the 61 fallacies covered in the book, only four of them are formal – and therefore invalid on their face. Two more can either be formal or informal – and the remainder are based on the content of the argument.

Consider the unfalsifiability fallacy. That is, someone makes an argument where it’s impossible to disprove the claim. This is what Sir Karl Popper used to identify the difference between science and pseudoscience. Science expresses its claims in a way that allow for them to be proven to be false, where pseudoscience appears beyond reproach.

This is a formal fallacy. You can’t make an logically sound argument that can’t be tested and proven incorrect. It’s not about the content of the argument, but is instead about its structure. Understanding how fallacies differ can help you spot them more easily. Of course, that assumes that you have a list of the fallacies you’re looking for.

The Listing

A friend of mine once spoke of spending hours outside looking into the sky looking for enemy aircraft flying overhead. In the middle of Michigan, this was a rather far-fetched idea; however, he was ready. He had his plane spotter cards and could identify the silhouettes of both American and enemy planes. He was prepared to identify the enemy and give report of their numbers. As amusing as this may seem, he was primed with what to look for so he could be ready. Here are the logical fallacies as laid out in the book, so you can be ready to identify them:

Person A makes claim P; person B states that A has a bad character; therefore, P is false.
Attacking a speaker’s argument by insulting the speaker.
Argument ex Concessis; Appeal to Motive; Vested Interest.
Person A claims that P. The circumstances of A discredit his assertion that P. Hence, we should disbelieve P.
Undermining the credibility of an argument by appealing to some facts about its proponent, where these facts are inconsistent with the proponent’s advocacy of the argument, or where they undermine the proponent’s credibility in putting forward the argument.
Opponent A argues that P. But a third party B also argues that P. B is unsavory. Hence, we should disbelieve that P. (Implicit premise: if B is unsavory, we should reject everything they say).
The proponent of argument P associates with B. But B is unsavory. Hence, we should disbelieve P. Attacking an argument by casting aspersions on people or organizations associated with either its proponent or the argument itself.
The proponent makes an argument P against a certain behavior or action Q; but the proponent himself engages in Q. Hence, we should disbelieve P.
Undermining an argument against a certain behavior or action on the grounds that the proponent himself engages in the very same behavior or action.
P is inferred from the major premise ‘if P then Q’ and the minor premise ‘Q.’
Substantiating a statement by showing proof of a tangential consequence.
An argument of the form “A is B, B is C, so A is C” (or similar), where the terms do not have a consistent meaning in the premises and conclusion.
An argument in which there is a term common to the premises and conclusion, or to more than one of the premises, but the term carries a different sense in each instance.
Argument P is justified by appeal to an authority A, whom the argument’s proponent does not (or cannot) name.
An argument’s proponent justifies it by appeal to an unidentified authority.
Argumentum ad Odium
The proponent justifies his argument for P by playing on the anger of the audience. Proponent A argues P. Opponent B states that P offends him, therefore P must be false.
Attempting to defend a position by exploiting the audience’s feelings of anger, bitterness and spite. Alternatively: attacking an opponent’s argument on the grounds that it angers you or your audience.
Argumentum ad Verecundiam
Person A claims that P. A is considered an authority. Therefore, P.
Attempting to support an argument P, not by offering any direct evidence that P, but by appealing to the testimony of an authority A.
Celebrity A believes that P. A is famous. Therefore, P.
Justifying a belief on the grounds that a celebrity believes it to be true.
Argumentum ad Populum
Everybody believes that P. Therefore, P.
Justifying a proposition on the grounds that many people suppose it to be true.
The Politician’s Syllogism
Situation S demands a response. Action P is proposed as a solution, where P is, in fact, irrelevant to S.
Demanding that an action be performed to resolve a situation, regardless of whether the proposed action will in fact resolve the situation in question.
Proponent A argues for or against conclusion P by invoking the emotional effects of P.
Arguing for the conclusion of an argument by appealing to the emotions of the audience, rather than addressing the matter at hand.
Proponent A has faith that P. Therefore, P.
Arguing for a conclusion purely on the basis of faith, rather than invoking any reason or evidence for its truth.
Argumentum ad Metum
Either P or Q. Q is frightening. Therefore, P.
P is presented in a way that plays on the audience’s preexisting fears. Justifying a conclusion by instilling fear against the alternatives in your audience. Alternatively: justifying a course of action by playing on the audience’s fears.
“God demands that P must be done. Therefore, P must be done!”
Justifying an action on the grounds that it has divine assent, in other words, that God wants you to engage in it.
Society S, or person P, has accomplished feat F. Therefore, society T, or person Q, should be able to achieve feat G!
Arguing that, because a person or society has achieved something great (for example, putting a man on the moon), another person or society should be able to achieve something else of similar stature.
P is natural, therefore P is good; or, P is unnatural, therefore P is bad; or, P is natural, Q is unnatural, therefore P is better than Q.
Grounding the value of something by appealing to its naturalness; in other words, claiming either that something is good because it is natural, or bad because it is unnatural.
P is normal, therefore P is good; alternatively, P is abnormal, therefore P is bad.
Judging whether something is good or bad depending on whether it is determined to be normal.
Argumentum ad Misericordiam, or The Galileo Argument
Argument P is justified by invoking the opponent’s pity.
Attempting to support a position not by offering any arguments or evidence in its favor, but by appealing to the opponent’s feelings of pity or guilt.
P is possible, therefore P.
Asserting that something is or will be the case on the grounds that it’s possible that it is the case.
Reductio ad Ridiculum
Proponent A argues that P. Opponent B undermines P by ridiculing it, without addressing the argument underpinning P.
Attacking an opponent’s argument not by addressing the matter at hand, but by resorting to mockery: for example, repeating his argument in a sarcastic tone.
P is traditionally believed to be true. Therefore, P. (Implicit premise: whatever has been traditionally believed to be true is true).
Arguing that something is true, or valuable, on the grounds that it is traditionally believed.
Argumentum ad Ignorantiam
Proponent A argues that P, on the grounds that there is no evidence that P is false; alternatively, he argues that P is false on the grounds that there is no evidence for P.
Justifying a conclusion by appealing to the lack of evidence that it is false; alternatively, assuming that something is false because of lack of evidence that it is true.
BASE RATE (Informal)
In determining the probability of an event E, the base-rate probability that E will happen is disregarded, and specific facts about the case are used instead.
Information about the overall probability of an event is ignored when estimating how likely it is to occur in a particular case.
Petitio Principii
Proponent A justifies P on the grounds that Q, and justifies Q on the grounds that P.
An argument whose premises assume the truth of its conclusion.
Population M has a sub-class m, which has characteristic P.
It is then inferred that M also has characteristic P. However, m is not representative of M. Where a general conclusion about a population is drawn from the behavior of a small sample, when the sample does not accurately represent the population as a whole.
Authority A states that P. Therefore, P.
Justifying an argument based on the say-so of an authority whose credentials have neither been examined nor questioned.
Evidence E supports P, evidence F contradicts it. Proponent A appeals to evidence E to prove that P, while ignoring evidence F.
Establishing a conclusion by means of evidence, but selectively citing only evidence that supports your conclusion, while suppressing any evidence which contradicts it.
P is justified by Q. However, Q could only be justified by accepting P. (Alternatively: P is justified by Q, which is justified by a number of other steps, which are ultimately justified by accepting P).
Arguing for a conclusion on the basis of a set of premises, where the truth of the premises assumes the truth of the conclusion.
Many Questions or Loaded Question Fallacy; Plurium Interrogationum
The speaker asks a question, which presupposes a number of facts P, Q, R, to which the respondent is not committed.
The speaker poses a question that contains a complex presupposition. The presupposition is not stated, but is required for the question to make sense.
A term common to the premises and conclusion has two distinct meanings, such that the first meaning is required for the premises to be true, but the second meaning is needed for the conclusion to logically follow from the premises.
When the conclusion of an argument seems to follow from the premises, but only by virtue of an ambiguity in the meaning of the words used in the premises and conclusion.
FAKE PRECISION (Formal or Informal)
Argument P is supported by quantitative evidence E, where E lacks the quantitative precision needed to legitimately support P.
Supporting an argument with numerical data that appears to be more precise than it actually is.
Whole W is comprised of parts p1, p2,…, pn. Since each of the parts has a certain property, it is inferred that the whole has that property.
Inferring that what is true of the parts of a whole is also true of the whole.
Whole W is comprised of parts p1, p2, and p3…. Whole W has property P. Hence each of the parts will also have property P.
Assuming that what is true of the whole is also true of each of its parts.
A is P, B is P. A is Q, therefore B is Q.
An analogy is established between two things, A and B. A and B both have the characteristic P; A has the characteristic Q; hence it is inferred that B also has the characteristic Q.
Proponent A offers a choice between P or Q, on the condition that one, and only one, of the two must be chosen; in reality, however, accepting both P and Q, or a third alternative R, are also viable options.
A choice is presented between two alternatives. The proponent presents this choice as exhaustive and exclusive: one of the options must be chosen; no third option is permitted or even entertained. However, in reality, these two options are neither exclusive nor exhaustive.
Each instance of a small sample of thing A has the property X. Hence, all instances of A have property X.
A general rule about something is inferred from a few instances of that thing.
Mother Knows Best
Proponent A justifies proposition/command P solely on the grounds that it is his assertion.
Proponent A justifies command or assertion P by simply positioning himself as an unquestionable authority on P.
A model M is used to make predictions about a certain domain D. However, M is defined with strict parameters that are not always present in D.
Taking a model of reality to represent reality, forgetting that the model is predicated on parameters with which reality quite freely dispenses.
LYING WITH STATS (Formal or Informal)
Proponent A attempts to support argument P with statistical data S, where S does not support P.
Supporting your argument by using statistical data in a misleading manner.
Two events, E and F, are thought to be causally connected in a supernatural way.
Thinking that two events are causally related not because of any reason or evidence, but because of a presumed supernatural connection.
P ought to be the case. Therefore, P.
Thinking that something is the case just because it ought to be the case.
Shifting Sands
Proponent A puts forward argument P. Opponent B insists that evidence E is necessary for P to be accepted. Proponent A produces evidence E. Opponent B now demands a new, more stringent standard of evidence E1 for P to be accepted. Proponent A accepts E as the standard of proof for P, but relaxes the criterion of proof to evidence E2 after realizing that the standard E1 cannot be met.
To raise, or lower, the standard of proof required for accepting an argument, after the argument has been shown to meet, or fail to meet, a previously agreed-upon standard of proof. More generally, to change the terms of the debate or argument after the debate or argument has begun.
(Statistical) Tests {T1, T2,…, Tn} are conducted to test hypothesis H. One test, Tm, shows some evidence that H is correct. Therefore, the results of the test are taken to confirm H.
Drawing significant statistical inferences from any positive or negative results gleaned from tests conducted on a multiplicity of groups or criteria.
Identifying a natural property P with the good.
Colloquially expressed: “P is ‘natural’, therefore P ought to be done.” Strictly speaking, this fallacy has to do with identifying a non-natural property, such as goodness, with a natural property, such as pleasure. More colloquially, deriving the fact that something ought to be the case from the fact that it is the case. More colloquially still: using standards derived from nature to determine what ought to be the case in human societies.
Proponent A puts forward a proposal P to solve a certain problem. Opponent B points out that P would not completely solve the initial problem, or would fail to solve other, related problems. Opponent B therefore rejects proposal P outright.
Criticizing a proponent’s solution to a problem on the grounds that it does not solve the problem completely; in other words, on the grounds that it falls short of an ideal solution to the problem.
An argument that states that P, therefore Q, when P does not in fact imply Q.
When one statement is presented as following from another, while it logically does not.
Proponent A argues that P exists, because there is no evidence that it doesn’t exist.
Asserting that something exists, on the grounds that its nonexistence cannot be proven.
RED HERRING (Informal)
Ignoratio Elenchi, the Chewbacca Defense
Proponent A and opponent B are arguing about a topic P. B raises topic Q, on the grounds that it is relevant to P; however, Q is actually irrelevant to P.
Attempting to derail an argument by bringing in considerations that are irrelevant or out-of-context.
Proponent A puts forward proposition P. Proponent B attacks a simplified or absurd version of proposition P.
Attempting to refute your opponent’s argument by drawing allegedly absurd consequences from his argument, which, however, only follow from a caricatured misrepresentation of his position.
Proponent A puts forward position P. Opponent B retorts that Hitler believed in P; therefore, we should not believe in P.
Dismissing your opponent’s position on the grounds that Hitler (or some other evil figure) believed in it; or that the policy he advocates was also advocated by the Third Reich.
Proponent A asserts a substantive claim P, such that no evidence can count against P, or that no opponent may raise an objection to it.
A substantive claim which its proponent presents in a way that admits of no refutation, either by preventing any evidence from counting against it, or by automatically dismissing the objections of an opponent.
A and B are discussing topic P. B (as is his wont) raises topic Q, where Q is irrelevant to P.
Where a contributor to an argument derails the discussion by raising a favored topic of his, despite this topic’s being completely irrelevant to the argument at hand.
Absurd Extrapolation, Camel’s Nose, Thin End of the Wedge
If A, then B; if B, then C; if C, then… Z!
Predicting that horrific consequences will follow from seemingly innocuous actions, through an incremental, step-by-step process. So, if we do A, this will inevitably result in action B, which will result in C … which will result in (typically horrific) action Z.
Proponent A agrees to a general rule P. P applies to B. A demands that an exception be made regarding P’s application to B, without giving grounds as to why an exception is warranted.
Agreeing to a general rule or principle about something, only to suspend it in a particular instance, without giving any good reasons for doing so.
Proponent A makes claim P. P does not come about. Proponent A claims that, despite appearances, P has actually come about “in a spiritual sense.”
Taking a claim (usually a prediction) to be satisfied, despite lack of visible evidence for it, by asserting that it has been satisfied in a “spiritual sense.
Proponent A puts forward argument P. Opponent B rebuts P by actually rebutting P’, which is superficially similar to, but importantly different from P. Opponent B takes his rebuttal of P’ as a refutation of P.
Misrepresenting an opponent’s argument, directing your attack at the misrepresentation, and taking this attack to refute your opponent’s real position.
SUNK COST (Informal)
Investor A has sunk n units of currency into project P. Although P has little chance of making money, A continues to sink money into it, because he does not want to give up on n.
Sunk costs are the resources invested in a project or venture which have become irrecoverable by any means. The Sunk Cost fallacy occurs when the investor continues investing money in a project, despite having little or no hope that it will make a return above funds already invested, because of a reluctance to let the initial investment go.
Proponent A makes a claim that P, such that there is no way of disproving that P.
A substantive proposition is expressed in such a way that it becomes, in principle, impossible to raise a counterexample to it.
Proponent A discusses word ‘P.’ Opponent B thinks that A is discussing the concept or object that P denotes.
Consequently, confusion arises. Confusing the discussion of a word itself with discussing the concept the word denotes.


The astute observer may note that there are many of these fallacies which are related – something that the book is quick to acknowledge. However, each fallacy has a slightly different structure. As that structure changes so do the responses to them. Being able to identify variations on a theme makes you more able to see the subtleties and to see what you need to do to Master(ing) Logical Fallacies.