According to Wikipedia, a fallacy is "the use of invalid or otherwise faulty reasoning, or 'wrong moves' in the construction of an argument". I'm curious, however, about how are some things that are technically "wrong moves" (don't follow logically) are fallacies (and therefore should be avoided) and some others are not. I mean, I could imagine simple things as inductive reasoning in a list of fallacies followed by a list of examples where inductive reasoning fails (maybe something like it is actually a fallacy, who knows? Not me, it's a long list, I didn't check them all). See, for example, the Post hoc fallacy. I would guess that scientists sometimes do use one thing after the other as at least an evidence of causation. Surely this isn't always truth. But should we tell scientist to stop thinking like this because it is "fallacious"?

I've been thinking a little about this. It seems to me that, although the lists of fallacies can be useful for educational porpuses, they can't be followed mechanically. Is it really that? Did I miss something?

(I'm not a philosophy student, I'm just interested in the topic, so maybe I lack some background. Thanks in advance.)

2 Answers 2


You are quite right that lists of fallacies are useful but shouldn't be followed mechanically. Informal fallacies, in particular, are often just rules of thumb, and it may be a contentious question as to whether they apply in some particular case. A claim that an argument is fallacious should always be accompanied by an explanation or justification of why it is fallacious.

Where the text refers to 'wrong moves' in an argument, I suspect the authors had in mind something broader than just cases where something doesn't follow logically. A lot of arguments are not intended to be deductive, but merely express the claim that the premises support the conclusion in some way. Such arguments are not 'valid' in the way logicians use the term, (or 'deductively valid' in some usage), but this does not make the arguments bad or fallacious. An abductive argument may be highly cogent, but fall short of being valid.

So, an argument may be invalid but not fallacious. Equally, an argument may be valid and fallacious. For example, circular arguments are valid, but they would usually be classified as fallacious.

People disagree over exactly how to define or recognise fallacies, but the two main criteria are:

  • Fallacies involve a defect in reasoning, i.e. they fail to meet the appropriate standards of good reasoning;
  • Fallacies have a tendency to mislead, i.e. they make an argument appear more persuasive than it should be.
  • Thank you for your response! And with a crystal clear reasoning! Good thing it was really that!
    – Jp_
    Commented Jun 11, 2021 at 1:48

When Philosophy textbooks explain about fallacies they refer to deductive reasoning only. Inductive reasoning is in fact what sciences use for the most part. Scientists can use deductive reasoning some times but in the end experience is preferred to just thinking.

Inductive reasoning is by definition uncertain. Inductive reasoning must use the five famous senses where as deductive reasoning does not need to technically. Just by using rules with no outside experience one can derive conclusions deductively. If the premises turn out true the conclusion must also be true with no experience needed. Science doesn't allow that at all.

Science requires experiments and induction is the means humans naturally learn by our senses. The five famous senses we all know about are hearing, smell, taste, sight, and touch. David Hume once argued that no science can produce CERTAINTY because experience is involved and our senses can be faulty. We can never be sure our senses are 100 percent accurate. Our sense can be fooled.

All modern scientists know knowledge can be updated coming into scientific research. They know some theories will likely be proven wrong. As a matter of fact they expect all sciences to be falsifiable. If a science is not falsifiable then that field is like a dictatorship where people are at the mercy of the leaders who also can possibly be wrong. So science could still be uncertain under no dictatorship or with a dictatorship of authority telling us how things in the world work. Either way science can't be certain. Scientists know this already.

When scientists reason inductively they do not commit a fallacy automatically because the conclusions derived by scientists are uncertain. The scientific conclusions are sometimes true and other times modified if an error is found. Inductive reasoning doesn't need to be certain as deductive reasoning does.

When we speak on fallacies we mean deductive reasoning and not inductive. One way to look at any fallacy be it formal or informal is that there is no guarantee or certainty to the conclusion. That is, sometimes the conclusion may be correct and sometimes that very same conclusion you arrived at moments ago or days ago may be wrong. It is correct on Monday but false on Tuesday. Validity must be brought up here be cause all fallacious arguments are invalid arguments.

Validity is the concept where the premises are so closely related that if the premises are true then the conclusion must also be true as well. That is, the conclusion is impossible to be false while the premises are true. So what makes a fallacy incorrect reasoning? Well if your premises are known to be true and you arrive at a false conclusion then you know something is wrong. The reasoning is unreliable. How will you know when you can trust the line of reasoning and when you can't? Will you make a mental note about what days of the week your reasoning arrived at correct conclusions and recall the days you didn't? You would have to remember a lot of material using this method.

All fallacies have names so we can categorize them. We categorize them because they are related in a close way. This is far better than memorizing all case by case variations about a particular topic or specific arguments. We can see a repeatable pattern with categories of fallacies. How do we spot a fallacy? We noticed certain things take place each time the fallacy is committed sort of like how a doctor can prescribe medication within 15 minutes or less after hearing the symptoms. A prior Experience in human history or a pattern has repeated in the medical professional's mind that he spots it quickly without spending too much time effort or asking 20 questions. This way he saves time and can move on to other tasks.

There are fallacies in the category of what is deemed as "formal" which have repeated patterns that are categorical or resembles mathematics; and we have what is deemed "informal" that are in semantic form which does not represent mathematical reasoning or categorical reasoning.

In reality most humans do not reason categorically as Aristotelian logic shows and we know humans don't typically break out paper and pen to write Mathematical looking arguments for people to follow. There is a reason this is not done in a legal courtroom!

For the most part in reality humans will often purposely commit fallacies to undermine another person. So for a fallacy to exist we have to know the conclusion does not always come out true with certainty. This is a pattern by itself all fallacies share. There may be other mechanical factors that bring up other types of patterns like in formal reasoning. We must first distinguish formal fallacies and informal fallacies. We don't lump them as one. In either case some pattern is formed which is how we as human beings recognize the error in reasoning. This is a way of pattern recognition. Once you know the classifications of types of fallacies you will notice patterns repeat and some patterns are special to types of reasoning. There is no mechanical way to generalize when any type of fallacy is committed.

  • thank you for your detailed and attentive response! I don't lack so much background and I don't think non falsifiable statements are dictatorship-like. But I see your point. Again, thank you!
    – Jp_
    Commented Jun 11, 2021 at 1:35

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