Bo Bennett's criteria distinguishing a logical fallacy from a pseudo-logical fallacy has three parts. The third part is:

  1. It must be deceptive in that it often fools the average adult.

Douglas Walton, after studying arguments from ignorance, claims that a fallacy in general is a tactic of deception: (page 270-1)

...a fallacy is a sequence of argumentation used in a context of dialogue (of which there may be many types) as a tactic of deception to trick a speech partner in an exchange, or as an underlying systematic, and serious type of error reasoning. Note that a fallacy, according to this conception, is not just any error, weak argument, or violation of a rule of dialogue, but a particularly serious and systematic type of error or sophistical tactic of an identifiable kind, used in argumentation to obstruct a goal of dialogue, or interfere with its realization.

This association of fallacy with deception, rather than rationality, puts it more clearly under ethics than logic.

I am looking for sources, not arguments except as they describe what is in the sources. I want to explore the association of fallacy with deception both for and against. Examples like Bennett and Walton would be on the "for" side.

Bennett, B. "Pseudo-Logical Fallacies" Logically Fallacious https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/6/Pseudo-Logical-Fallacies

Walton, D. (2010). Arguments from ignorance. Penn State Press.

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    What distinction are you making between deception and rationality. Deception, when purposeful, is totally rational -- it just seeks a goal other than mutual understanding. Controlling other people is a rational goal. Controlling them may well be in their best interest. Cultures are built on mythologies, after all. (Take this in the vein of Nietzsche's "We have yet to properly esteem the power of a lie.") When not purposeful, it is not really deception, is it? It is simply delusion or error.
    – user9166
    Dec 10, 2018 at 18:14
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    @jobermark Walton claims that Eemeren and Grootendorst (I couldn't find the reference in his bibliography) is a violation of a rule of a critical discussion. This would be an example that does not include deception. I agree that a deceiver is being rational when implementing the deceit. What I think is the claim is that without deception there is no fallacy. Dec 10, 2018 at 18:54
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    @guest271314 I am not looking for examples of deception, but philosophical considerations of the idea of fallacy as a process of deception (or not). That is, philosophical views that would argue that without deception there is no logical fallacy. When I ask for sources I am looking for references where the arguments are being made. I don't want an argument alone as an answer. Any answer should include a reference. Ethics are involved because the use of deception may be viewed as unethical, not simply illogical. Dec 10, 2018 at 18:58
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    I understand you don't want an answer without a reference. But there are clearly times when someone has deluded themselves into accepting a fallacy, in which case there is no deception in the moral sense, only error. It is not immoral to spread your incorrect understanding if you think you are being helpful. My question above was meant to imply you need a more narrow definition of 'deception' before you can really get an answer. Sorry to be wordy and indirect, that is just the state I am in...
    – user9166
    Dec 10, 2018 at 20:42
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    @jobermark I used to think fallacies where forms of incorrect understanding or irrationality, but reading Bennett and Walton I think they are forms of outright deception. But I am not sure and that is what is motivating this question. The deceivers, however, may be themselves deluded especially about their right to deceive others and they may even believe what they are saying for the most part. But deceiving others would be an ethical failing not a logical error. So, a fallacy requires (1) an argument and (2) a deception before there is a fallacy from this perspective. Dec 10, 2018 at 23:06

2 Answers 2


Let me make a case for the "against" side.


0.1 I won't use the Oxford English dictionary because it's behind a paywall.
0.2 I'll put a bibliography at the bottom of the post.
0.3 I've struggled with the formatting. I apologize if it makes the post difficult to follow.

1. Merriam-Webster's (hereafter "the dictionary") 3rd definition for fallacy is:

An often plausible argument using false or invalid inference

There is no mention of deception (in the 3rd definition).

2. Lews Vaugh, in The Power of Critical Thinking offers another defintion of fallacy without using the word deception:

An argument form that is both common and defective, a recurring mistake in reasoning (p. 561)

3. Both of these are consistent with the definition of a valid argument provided in The Logic Book:

An argument is deductively valid if and only if it is not possible for the premises to be true and the conclusion false. An argument is deductively invalid if and only if it is not deductively valid (p. 11)

(3B) Note: the, The Logic Book does not use the word fallacy, but it does use the phrase "invalid argument" and talks about errors of inference. By the dictionary definition quoted above, that is a fallacy.

(3C) Deception is not mentioned (in this particular definition, or in The Logic Book at all, because the authors seem to believe you can make an invalid inference by mistake).

(3D) Remember that the goal of logic is truth preservation - a valid argument will never start with premises that are all true and lead you to a false conclusion (The Logic Book , p. 1). It can protect you against both subterfuge and mistakes. It's designed for both.

  1. In closing:

Bennett says on his website that a fallacy "must be deceptive." In this context 'must' suggest 'necessity'.

To say that deception is necessary for a fallacy implies that it is not possible to have a fallacy without deception. The dictionary and Vaughn offer two definitions of fallacy that are consistent with the formal understanding of validity provided in The Logic Book and depict a scenario where a fallacy can occur without deception and I submit them as a counter-example to the claim that fallacy necessarily requires deception.


Lewis Vaugh,The Power of Critical thinking, 5th ed (New York: Oxford University Press, 2016).

Merrie Bergmann, James Moor, and Jack Nelson, The Logic Book, 3rd ed (New York: The McGraw-Hill, 1998).

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    Bennett is talking about informal fallacies not formal fallacies. I agree with you that formal fallacies are best viewed as mere mistakes, perhaps like spelling mistakes. They are not deceptive. But informal fallacies used in natural language arguments can be the result of one side trying to deceive the other. Here is where I see an ethical issue arising. But sometimes people deceive themselves. When that happens it can't be described easily as an ethical issue. I thought the deception in informal fallacies implied an ethical issue, but I see that I was wrong. +1 May 16, 2019 at 1:32
  • I agree with you that often informal fallacies are used deceptively. But Bennett misses that sometimes people are truly ignorant. They think they have presented you with a brilliant argument and then get really upset when you try to explain to them why it's fallacious. Some seem to lack the capacity to understand, and some seem go into denial, which may fall under self-deception. But we don't want everyone running around deceiving themselves saying "Well, I have the right to my opinion" At that point can we say they have failed in their (moral) duty to seek the truth? idk. It's a good question
    – Rob
    May 16, 2019 at 3:40

jobermark observes in a comment:

But there are clearly times when someone has deluded themselves into accepting a fallacy, in which case there is no deception in the moral sense, only error. It is not immoral to spread your incorrect understanding if you think you are being helpful.

Douglas Walton and Marcin Koszowy consider the argument from authority to be

a dangerous one that can go wrong in some instances and be quite deceptive as a rhetorical tool for strategic maneuvering in argumentation. (page 1 in pdf)

However, this deception could come from two different sources:

Hence there is a normal tendency for the recipient of the argument to be overly intimidated by it, and to presume that it would be inappropriate to raise critical questions about it. So the fallacy in such a case resides in the reaction of the recipient to such an argument, but it may also arise from the way the proponent of the argument puts it forward. (page 5) [my emphasis]

It is possible for the deception to not originate from the way the proponent of the argument puts it forward, but from the recipient's own sense of intimidation preventing the authority from being questioned.

This suggests that jobermark is correct that there is no ethical issue involved with this deception.

Walton, D., & Koszowy, M. (2014). Two kinds of arguments from authority in the ad verecundiam fallacy. Two Kinds of Arguments from Authority in the Ad Verecundiam Fallacy.

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