My Debating Advice

Being able to argue properly and rationally with other people is very important in life. If you know how to structure an argument correctly, and what fallacies to look out for, you will avoid being deceived or out-spoken by scams or faulty logic, and you will avoid making these mistakes yourself, which increases the credibility and force of your arguments.

The following are fallacies to look out for which are very common. But even more important than being able to spot fallacies is the following: always realise that you can be wrong. The strength of your convictions is irrelevant to their validity.

Also, it is important to recognise the difference between a valid argument and sound argument. Valid arguments are structurally correct in that no formal fallacy is committed, but this doesn’t make them true. A sound argument is one that is valid and deductively true. E.g.:

P1: Socrates is a man.

P2: All men die.

Conclusion: Therefore Socrates will die.

Circular Reasoning / Begging the Question

People use the expression “which begs the question” in everyday speech when that they really mean is “raises the question”. To beg the question is actually a logical fallacy whereby your premises entail the conclusion, and the premises are dubious and implicitly assume that conclusion.

I will use two examples taken from the Skeptic’s Dictionary:

P1: Abortion is the unjustified killing of a human being and as such is murder.

P2: Murder is illegal.

Conclusion: Abortion should be illegal.

Abortion should be illegal if it is murder. This is a tautology. No one would dispute that. But notice how the first premise assumes that abortion is indeed murder. This must not be assumed, but proven. There is no proof that abortion is the killing of a human being.

Begging the question is not a formal fallacy because the argument is valid, in that it is not illogical and the syllogism is correct. But the argument is not sound because the first premise is dubious.

Another very common example of begging the question is the argument from design used by theists.

P1: The universe exhibits examples of design.

P2: Where there is a design there must be a designer.

Conclusion: Therefore the universe was designed (ergo god).

There is nothing wrong with Premise 2. The conclusion is also valid based on the premises. But the argument is still circular reasoning: it assumes the universe exhibits design, but this must be proven not assumed. The assumption is that design exists, but isn’t that what the argument should be proving?

Argument from incredulity / lack of imagination fallacy

“You’re not telling me that humans are descended from single-celled organisms! I can’t believe that!”

Someone’s inability to imagine a scenario is not an argument against it.

Argument from ignorance

In this fallacy, lack of evidence for a contrary viewpoint is taken as evidence in favour of another viewpoint. (Contrary is not the same as contradictory.)

e.g.: “It’s impossible to prove that God doesn’t exist!” one might say. Well, yes. But what does that prove? It’s impossible to prove that there isn’t a deity called the Flying Spaghetti Monster, but that doesn’t mean that it does exist.

In law, a person is assumed innocent until proven guilty. Even if there is no particular evidence that someone is innocent, that doesn’t make them guilty, e.g.:

“No one can prove that Tobe wasn’t at the scene at the time of the crime.”

This proves nothing. Evidence that Tobe was at the scene implies guilt. Anything else is circumstantial at best.

Argument from popularity

This is where someone argues that something must be true or false simply because of the number of people who believe it. However, the number of people who believe something is irrelevant to its veracity. E.g.:

“Billions of people throughout the world believe that god has touched their lives; therefore there must be a religious explanation.”

The fallacy is even more obvious when we say something like: “at one point, everyone thought the earth was flat.”

Indeed, a petition of 600 scientific signatures attesting that evolution couldn’t account for the complexity of life was replied to with a petition of 7000 scientific signatures that said that it could. Whether the petition had 601 or 6 million signatures is irrelevant. The sheer weight of believers on its own means nothing. What matters is whether the evidence supports evolution, not how many people believe it.

False dichotomy

This is also known at the false dilemma, bifurcation, the either-or fallacy, or the fallacy of the excluded middle. E.g.:

“If you’re not with us, you’re against us.” Or:

“If you’re not opposed to the death penalty, then you think criminals should get away with anything they do!” Or:

“Either all life arose by random chance, or it was specially created by god.”

The fallacy is to provide only two possible scenarios when in reality there may be many.

In the fallacious examples above:

1. It’s possible to be neutral and on neither side.

2. Rejection of the death penalty doesn’t mean at all that one opposes punishment and justice.

3. There are at least two other possibilities: life arose by non-random slight successive modifications, ever increasing in complexity. Or, god created life and allowed evolution to happen.

Ad hominem

This is an often misunderstood expression. It does not mean insulting or slandering the opponent. What it means is arguing against someone’s point of view based on that person, instead of their argument. E.g.:

“Joey Noname is a convicted sex offender, so what he has to say on politics is irrelevant.” Or:

“How how you be opposed to eating meat, aren’t you wearing leather shoes?!”

Hypocrisy is always good to expose, but it doesn’t prove anything. I could provide a perfectly sound argument in favour of vegetarianism, whilst eating a greasy quarter-pounder. You might think me hypocritical, or even a liar, but it wouldn’t necessarily mean my argument was wrong.

In Conclusion

What makes an argument right or wrong is its soundness. And of course, there is no substitute for proof or evidence.

The above are a few examples of fallacies that I frequently encounter when debating with people. There are of course many more.

Apart from the above, another great piece of advice is to know your own position, and know that of your opponents. There is no substitute for knowing what you’re talking about and knowing the counter-arguments, otherwise not only might you simply lose the debate, you’ll probably embarrass yourself.

Being a good arguer is about being logical, knowing fallacies, and having knowledge of the subject. Above all, personal biases and emotion are irrelevant. Our most cherished beliefs might be lies. Being a good debater is about wanting truth, whatever that may be.


15 Responses to “My Debating Advice”

  1. tobe38 Says:

    Good post. And I’m honoured to be given the starring role of the criminal in your example. I won’t read into that too much…

  2. D Says:

    Just a thought in the middle of that: Since when was killing an unborn baby NOT a murder of a human being?

  3. John P Says:

    Wait! Don’t start until I get some popcorn. I’ll be back.

  4. Darren Says:

    D, before we start, can you define the terms “murder”, “baby” and “human being” which we will be using, please?

  5. Darren Says:

    (I’m just illustrating a point. I don’t intend to get into this subject here.)

  6. evanescent Says:

    I agree with Darren, before we go any further D, please define the terms that we are going to be using.

    After all, none of us would want to ‘beg the question’ in an article on logical fallacies! 😉

  7. evanescent Says:

    I’ve just realised D that you might have missed the point here:

    Just a thought in the middle of that: Since when was killing an unborn baby NOT a murder of a human being?

    I personally have no problem with abortion, but that’s not the issue here.

    The example above is not saying that abortion is right or wrong, but the argument used begs the question because it ASSUMES what it should be trying to PROVE. This makes it fallacious, regardless of whether you agree with abortion or not.

  8. Kristi Collins Says:

    great post. I needed to understand this better.
    Oh, and I used it to argue my point here:
    I put a link to your blog when you click on fallacy.

  9. evanescent Says:

    Hi Kristi,

    I’m glad you found the article useful, and I’m glad you decided to link to it on such a worthwhile blog as your own.


  10. Spanish Inquisitor Says:

    Here’s a couple of other good sites for debaters.

    The Nizkor Project

    The Fallacy Files

  11. D Says:

    I should have been more clear. I’m not trying to start a debate, I’m just making a point. Don’t include me in this.

  12. Medical News » Are new age therapies leading us away from evidence and reason? Says:

    […] good — that still does not mean that alternative treatments are the answer. This is called a fallacy – because lack of evidence for a contrary viewpoint cannot be taken as evidence in favour of […]

  13. Tanya Says:

    Actually, I dug out my philosophy textbook and it states that an ad hominem is “instead of debating the issues, you attack your opponent personally”
    Experiencing Philosophy by Anthony Falikowski

  14. evanescent Says:

    Actually Tanya, an ad hominem fallacy is not where one just attacks somebody personally – that is, it isn’t a synonym for “insult”. The ad hominem fallacy occurs when one attempts to win or disprove an argument by using something about the other person as a reason.

    For example: “Tanya is a theist, so her opinions on philosophy are irrelevant”. That is an ad hominem fallacy, though not necessarily an insult.

    Here’s a good article which explains the difference:

  15. Burgess Laughlin Says:

    I don’t see a conflict between posts 13 and 14. The key word in Tanya’s quoted definition is “instead.” And I agree with Evanescent’s characterization–“… one attempts to win or disprove an argument by using something about the other person as a reason”–if we add: “where that ‘something’ is not relevant to the argument.”

    If I say, “Teebone Smith is immoral because he is dishonest and dishonesty is immoral,” I have used something I know about the person as a reason for my conclusion. My argument is valid in form.

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