What imparts to informal fallacies their fallacious nature?

I have been reading Wikipedia because of the ease of access, as well as some references listed there, like https://www.humanities.mcmaster.ca/~hitchckd/25.pdf

The criticism of informal logic appears persuasive.

To better understand my question about what imparts to informal fallacies their fallacious nature:

I am asking why informal fallacies are fallacious. What is the essence of their fallaciousness. Probably providing a minimal set of necessary and sufficient conditions would be helpful but I would need to know exactly why informal fallacies meet those conditions.

As for the paper I did not claim it critisized informal logic. I plainly said that I read it.The paper's lack of systematicity for one was a big blow to persuading me. On the other hand the motivation of informal logic "dealing with arguments in highly charged debates" is not one to be able make a field stand alone. Phillosophy of communication would be much better accepted as it is much better equipped. It does not only address arguments but communication in general. Secondly when evaluating arguments you are measuring how persuasive they are you could not deal with truth in any other way than formal logic's soundness.

I would enjoy reading exactly what is not clear abour my question

What imparts informal fallacies with their fallacious nature?

and why.

  • 1
    I am not clear about what you are asking. Jan 26, 2020 at 2:56
  • 2
    Fallacies are mistakes in reasoning, informal fallacies are mistakes in informal reasoning. The absence of formal theory is quite common in soft sciences, so Massey-style criticisms are generally not taken seriously. I am also unclear what you are asking.
    – Conifold
    Jan 26, 2020 at 3:59
  • Is the question, perhaps, about the "essence" of fallacious reasoning? That is, do you want us to produce something like a minimal set of necessary and sufficient conditions for something to count as a fallacy?
    – Schiphol
    Jan 26, 2020 at 16:51
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    Overall, even biology lacks it, although typically counted as a hard science. There are, of course, some formalized models for special examples, but Toulmin et al. developed that for informal argumentation as well. The ideal of science on the prototype of mathematics and physics has been abandoned since the time of Massey's writing, as it is unworkable beyond them.
    – Conifold
    Jan 27, 2020 at 2:03
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    Formal theory is typically something like quantum mechanics, not a loose collection of specialized mathematical and not so much models like "consumer theory", etc. But again, if that counts as "formal theory" there is Toulmin's argumentation theory, and many others. Modal, deontic, epistemic, doxastic, etc., logics were also developed to model informal arguments.
    – Conifold
    Jan 27, 2020 at 3:36

2 Answers 2


You can say that the essence of formal fallacies is that all of them are non-sequitur. In essence there is only one formal fallacy -- making a deduction that appears to be warranted by formal logic, but isn't. Arguing from the consequent is the clearest example, it just uses an axiom backward. But at a higher level, how you inject the confusion is irrelevant, you have made a deduction step that is not a deduction.

The corresponding essence informal fallacies is irrelevance. To some extent all of these are instances of the formal fallacy of 'argument from ignorance'. All of them inject distracting irrelevant content, hide relevant content, or by using a pair of fallacies together, disguise relevant as irrelevant or irrelevant as relevant information. Ad hominem injects irrelevant social norms; jumping to conclusions hides relevant information behind the convenience of having a solution in hand; all the forms of "bad math" offer a flawed analogy in place of an applicable model. So again, there is a lot of detail, but in the end they all involve drawing a conclusion from irrelevant material, which is the argument from ignorance, which is a non-sequitur.

  • There are many examples where I do not see the irrelevance. The definitist fallacy. Moving the goalposts. Proving too much, Fallacy of many questions. Feb 18, 2020 at 20:38
  • The new definition is relevant? The new demand is relevant? The expanded framing is relevant? The extra questions are relevant? If they are, then that is not a fallacy, it is a real argument. Feb 19, 2020 at 3:02


Formal and informal fallacies are both persuasive forms of incorrect reasoning. Formal fallies are easy to identify because the structure of the formal language is what linguists called surface structure. For instance, a simple formal fallacy goes as such:

P1 A implies B
P2 B
C Therefore A.

If we want to see a natural language version (glossing over some attacks on implications arising from intuition), it goes as:

P1 If Socrates is in the kitchen, then he is in the house.
P2 Socrates is in the house.
C Therefore, Socrates in the kitchen.

If one thinks through this circumstance, it's obvious that the reasoning is specious.

A formal fallacy is easy to identify because once translated into a formal language, the surface structure is mapped to a particular name. In the case of the argument:


the fallacy is known as affirming the consequent. Formal fallacies thus exist by essence of their logical form which can be identified syntactically as opposed to their semantics. Formalists love formal discourse because truths are determined relatively independent of meaning and thus are almost understandable of being free of normativty. Definitions suffer from near-universal consent (except from geniuses and cranks.) The ALU/CU of a typical machine can churn through these statements embarrassing humans in their proficiency.


Informal fallacies are also persuasive but logically incorrect, however, they rely on the deep structure of language. Searle calls it the Background. Computer scientists often just call it common sense. In essence, the dream of many linguistic formalists is to create an entire theory to describe these transformations. X-bar theory in the vein of Harris-Chomsky-Jackendoff is one example of how truth and meaning are interconnected through a series of formal grammars that attempt to explicate a natural grammar. Natural language processing and various schools of linguistics, including cognitive linguistics and psycholinguistics has greatly enriched the philosophy of language (though many logicians continue to work independently of the science).

So, to address your question:

What imparts informal fallacies with their fallacious nature?

This is a good question, and many who prefer formalisms sometimes struggle to understand the nature of the informal fallacy. I'll draw from Attacking Faulty Reasoning by Damer. From the chapter Introduction:

An informal fallacy is a misleading argument ("a group of statements, one more of which... the premises... support or provide evidence for another... the conclusion) whose statements violate one or more of three criteria:
1. Acceptability
2. Relevancy
3. Grounds for truth of conclusion

Well, you can see why formalists hate such definitions. They are highly normative. What is an acceptable proposition? How do you determine if the proposition is relevant? What does it mean to have adequate grounds for a conclusion? How do you tackle drawing inferences from natural language in which anaphor, metaphor, metonymy, synonymy and other figurative expressions play a heavy role in determining meaning? This isn't a small problem. This is the problem of grounding meaning in symbols, and is at the heart of why the Turing Test works to separate wheat from chaff, and plays prominently in the debate over the Chinese room.


One philosopher who plays a prominent role in attacking formalism and advocating natural language philosophy is Stephen Toulmin who explored practical argumentation, not the toy problems of mathematicians, but the real-world kind that play a function in society. In his Uses of Argument he dispatches with the pedantry of logicians and looks to Anglo-American tradition of law for inspiration. He advocated a certain model with terminologies such as warrant, backing, rebuttal, qualifier, and domain-specific implying the importance of ontological pluralism and epistemological diversity in metaphysical presuppositions.

The ordinary language philosophers, such as Ryle, were/are big on stripping down language to common-sense positions and looking at praxis for determining truth. It might be understood as an empirical take on the philosophy of language setting aside the metaphysical speculation of logicians and embracing the self-evident truths of day-to-day life.

Now, to address the other part of your post. The thesis of the paper is that informal logic is not given it's due and that there are two major scandals involved. From page 6:

It is a scandal that the organizers of the World Congress of Philosophy can include sections on [various topics], but have not got around to including a section on the philosophy of argument.

This is important, because as a relatively upstart field informal logic is much better posed to address irrationalities such as "ideological fanaticism to culpable ignorance, and informal logic squarely faces this problem". Also:

... the teaching of informal logic in undergraduate philosophy courses in North America remains mired in antiquated theoretical conceptions, long disproved or at least questioned in the theoretical literature...

Is the criticism in the Wikipedia article enough to derail the subfields continued growth? Not according to the author of the paper who you present who makes a great case that after 50 years, there's been an explosion in interest and publication in the topic, and that further inroads can be made to strengthen the discipline such as addressing the two scandals listed.

  • But I did not say that paper I listed criticized informal fallacies. I said that I read it. By saying that I read it I meant that even though I read it it did not convince me. The critisism was en.wikipedia.org/wiki/Informal_logic#Criticisms. Jan 26, 2020 at 23:48
  • @GeorgeNtoulos I see what you intended to communicate in the post now, sorry. I'll amend.
    – J D
    Jan 27, 2020 at 4:07
  • @GeorgeNtoulos Okay, I read Massey's article as well; so what is it that Hitchcock's article didn't convince you of. You don't state.
    – J D
    Jan 27, 2020 at 16:51
  • The paper's lack of systematicity for one was a big blow to persuading me. On the other hand the motivation of informal logic "dealing with arguments in highly charged debates" is not one to be able make a field stand alone. Phillosophy of communication would be much better accepted as it is much better equipped. It does not only address arguments but communication in general. Secondly when evaluating arguments you are measuring how persuasive are they you could not deal with truth in any other way than formal logic's soundness. Jan 29, 2020 at 15:56

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