Fallacy: How To Really Understand It?

Fallacy is a term that is often used in the intellectual circles in the context of science. People usually use the term to discredit an argument or point out flaw(s) in an argument. As the term has gained popularity over the years, I often observe people misusing the term.

This is a classic example of a scientific term that is slowly turning into mainstream jargon. Which is absolutely fine; I have no complaints there. However, I see an issue with using “fallacy” loosely in a scientific context.

To counter this issue, I thought I would cover the formal meaning and usage of the term. In this essay, I will start by differentiating between informal logic and formal logic. Next, I will proceed to cover the notion of syllogisms.

Finally, I will build on top of the aforementioned concepts to give you a clear picture of how a fallacy is formally defined and used. Let us begin.

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The Difference Between Mainstream Logic and Scientific Logic

Imagine that you and your friend are having a heated argument about something, and she says the following to you:

“Your logic sounds good to me, but I can’t help the feeling that you are missing something.”

The “logic” that your friend refers to here is informal logic or mainstream logic. It is inductive in nature and is subjectively lenient when it comes to the burden of proof. If you find a way to “convince” your friend, she is likely to “accept” your (informal) logic (or vice versa).

In the worlds of philosophy and mathematics, logic works differently. The term “logic” formally refers to a system of deductive reasoning based on a set of premises. This system places strict requirements on the burden of proof.

Informal logic focusses on the application of knowledge (both learned and empirical) to analyse a situation/problem and arrive at a conclusion. Formal logic, in turn, focusses on the structure of an argument (in an abstract sense) to evaluate if a conclusion is valid or invalid.

While we only have a finite number of argument structures in the formal setting, the informal setting features the freedom of infinite pathways. In this essay, we are focussed on formal logic in the context of science.

More precisely, we are interested in the validity of logical arguments. To understand how this works, we need to understand another technical term known as a syllogism.

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The Road to Understanding Fallacy — What is a Syllogism?

A syllogism is a form of logic that typically involves a major premise, a minor premise, and a conclusion that is deduced from the premises. It is perhaps more efficient to see an example of this in action first:

As you can see, the conclusion is deduced from the information provided by the major premise and the minor premise. The major premise provides a broad setting, whereas the minor premise provides a narrow observation relative to and related to the major premise.

The conclusion, then, is logically deduced from the two premises. The conclusion in syllogisms could either be valid or invalid. A conclusion is valid if it necessarily follows from the premises.

In other words, if the premises are true, there has to be no other alternative other than one conclusion for it to be valid.

If the conclusion does not necessarily follow from the premises, it is an invalid conclusion. Now that we have covered what a syllogism means, we are ready to proceed to the notion of fallacy.

Fallacy — Formally Defined

A fallacy is nothing but an invalid argument. At this point, you might be thinking:

“Is that all it is? Then why in the name of Jupiter did you make me read ALL this text?”

If you are indeed thinking along these lines, I request your patience and focus. Focus on the “invalid argument” part. It is ridiculously easy to mistake these two words for their informal or mainstream meanings.

The scientific/logical notion of fallacy only conforms to the logical/syllogistic definition of “invalid argument”. Consider the following example:

Here, the conclusion is invalid, and therefore, fallacious. The reason is that All A’s could be B’s that are NOT C’s. If this example is too abstract for you, here is a (non-equivalent) relatable example:

In this case, while Sally likes SOME animals, it does not necessarily follow from the given premises that Sally likes Damian (the dog). Hence, the conclusion is fallacious.

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Closing Comments

In the real world, arguments are not often as clear and simple as the Sally/Damian example. Also, the partition line between formal and informal logic is also not very clear. But what is clear is that when arguing in the context of science, one should stick to formal logic and require other participants also to do so.

Even in an informal setting, with enough practice, you will start noticing patterns repeating. With sufficient knowledge and experience with forms of (formal) logical arguments, you would be able to easily evaluate the validity of arguments.

Personally, this works so well for me that I often feel like I have an unfair advantage compared to most (uninitiated) folks when it comes to arguments.

But focusing on the goal of this essay, you will be able to tell clearly when the term “fallacy” is used in the mainstream sense in a scientific context. That way, you can spot a pseudoscientific argument coming from afar!

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Reference: James Fieser, Bradley Dowden, et al.

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Further reading that might interest you:

• How To Really Understand The Philosophy Of Inferential Statistics?
• How Easy Is It Really To Predict The Future?
• Correlation: One Of The Most Misunderstood Concepts In Science.

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