The idea of a two-edged sword, or a sword that cuts both ways, has a storied history. The analogy is somewhat problematic, as swords always have two edges anyway, and it is in doubt that a trained swordsman is going to be constantly cutting himself with his own sword. But regardless, we know what it means. It’s a self-defeating or self-refuting idea, where an idea basically falls on its own sword (OK fine, I’m done with the sword puns). My contention is that these ideas are more common than we probably realize. I believe it’s important, for the sake of a better-informed society and more intelligent conversation, that we drop some of these ideas.
So what makes for a self-defeating idea? Let’s look at 10 examples:
1) All truth is relative.
If all truth is relative, then this statement is also relative, and can’t apply to anything beyond itself. The statement therefore becomes almost meaningless!
2) No one can know the full truth about religion.
This seems like a great and humble statement about religion. Of course it’s arrogant to say you know the full truth about religion, that somehow you have a full and truer view of the world than someone else. So what’s the problem and why am I bringing this up? The problem is, that statement is actually claiming a ‘full truth’ about religion. It’s like saying that there is no such thing as an English sentence.
3) You need for there to be a God.
I’ve heard this before. People think that religions believers need God as a kind of psychological crutch to face the terror of death. But this statement won’t do the trick, for a number of reasons. First, the origin of a belief doesn’t really have anything to say about the truth value of the belief. Second, saying something about someone’s psychological state goes both ways. You say people need there to be a God, I say you need for there not to be a God. The point is: Someone’s needs or desires often having nothing to do with the truth of a particular idea or statement.
The next one’s fun, it’s a pretty popular maxim that I actually found repeated at the start of my logic textbook (how ironic!).
4) “It is wrong, always, everywhere, for anyone to believe anything on insufficient evidence.” – W K Clifford
What evidence is there that we should believe this? There’s no evidence here for that statement being true – therefore we shouldn’t believe this statement.
5) Science is the only reliable guide to truth.
The problem: This isn’t a scientific statement, so we can’t trust that this statement is true!
6) You should doubt or be skeptical of everything.
Therefore I’m doubtful and skeptical of this statement!
7) You can’t know anything for sure.
Do you know that for sure?
8) Belief in God is a projection of your culture.
That belief about religion is a projection of your culture.
9) Determinism is the only way to understand the world.
You have to draw out the implications of determinism to show the problems of this view (also, I’m referring to hard determinism here). By making this statement, you’re trying to change someone’s mind. Why bother if it’s determined? Also, to count as a rational belief the belief must be chosen, which is impossible on a deterministic account.
10) Naturalism and evolution are true.
This is a bit more indirect, and much more heavily disputed. The key idea is that when these two ideas are combined, you undermine the reliability of your cognitive faculties. If the brain and how it thinks have just evolved from fight to survive mechanisms, then we don’t have any reason to suggest the brain comes to true beliefs, just beliefs helpful for survival. Therefore, by saying that both naturalism and evolution are true, you undercut the reliability of your cognitive faculties. This is a far more complex argument to do justice to within a short paragraph, feel free to hold this one in suspension until I return to it at a later date.
If you’ve believed some of these ideas before, I would encourage you to either refine the way in which you think about the idea, or drop it completely. Can you think of any other self-defeating ideas?
think-well.org 
October 25, 2016 at 2:43 am
Reblogged this on Would You Consider? and commented:
Skeptics keep us honest.
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October 29, 2016 at 3:28 pm
Thanks!
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October 26, 2016 at 10:24 am
Why do you say that “to count as a rational belief the belief must be chosen”? It doesn’t seem to me that ANY of our beliefs are chosen. When I see my cat sitting on the couch, I don’t choose to believe he’s sitting on the couch. I’m caused to believe it just by seeing it. I couldn’t choose to believe otherwise even if I wanted to. If I hold a belief because the evidence was so compelling that I could not believe otherwise, then does that mean my belief is not rational? That strikes me as being counter-intuitive because it would mean the stronger our grounds for believing something, the less rational we are for believing it. After all, the stronger our grounds for believing something, the harder it is not to believe it, and the closer those grounds are to determining our belief. Does that seem backward to you? So why do you think a belief has to be chosen before it can be rational?
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October 29, 2016 at 4:14 pm
I want to make sure I’m understanding you correctly. So you don’t think we choose our beliefs, and that there’s some kind of causative element from our sensory perception that is so strong that you COULDN’T believe otherwise? Say, even if you were shown incontrovertible evidence that you’re a brain in a vat or something of the like? That seems problematic to me, but I’ll try and clarify what I mean and hopefully that will clear things up.
I said ‘belief’ when I probably should have said knowledge (but they are fairly commonly equivocated) – I was referring to the typical JTB analysis of knowledge, where a belief should be justified, true, and chosen as a belief for it to count as knowledge.
“If I hold a belief because the evidence was so compelling that I could not believe otherwise, then does that mean my belief is not rational?”
Of course not! That’s not what I’m saying here at all.
The point I’m making here is that if you’re going to try and convince someone that hard determinism is true, it seems relatively pointless as their belief in determinism would already have been determined. So by trying to convince someone, in an indirect way you’re kind of pragmatically saying that determinism isn’t true, or that you don’t mind being a choiceless agent in a causal chain.
I know brevity sometimes means you lose nuance. Hopefully that clarifies what I mean here. Thanks for the questions!
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October 26, 2016 at 4:58 pm
Nice article. Thanks for putting green it together.
I must take issue with #5, however, as the assumption is that science is infallible. Science has exposed many truths, but science itself relies on human observation, which can be fallible.
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October 29, 2016 at 4:13 pm
Thanks so much for the feedback! That assumption isn’t what I was focusing on in this post but it’s certainly a helpful one – always good to remember that humans are involved in the process of doing science!
I was more critiquing the idea of scientism in this post, as it’s a philosophical statement (and not a scientific statement) to say that science is the only way we can know truth – and therefore self-refuting.
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October 27, 2016 at 4:31 am
Very thought provoking. There are a lot of personal self defeating beliefs also
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October 29, 2016 at 4:15 pm
Glad you liked it! Are you referring to psychological defeaters, like cognitive biases? If so, I’m actually doing an article on that right now! I’ll be posting it within the week!
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