Argument from incredulity
Bad Moves: Arguments from incredulity
By Julian Baggini - original
"No one in their right mind can look in the stars and the eternal blackness everywhere and deny the spirituality of the experience, nor the existence of a Supreme Being. There were moments when I honestly felt that I could reach out my hand, just as the pilot John Magee says in his poem 'High Flight', and touch the face of God."

Eugene Cernan, last man to walk on the moon (Source: Observer Magazine, 16 June 2002)

These few lines are stuffed full of argumentative bad moves. There's the ad hominem abuse - people who disagree are just not in "their right mind". There's also a whiff of the argument from authority: an "I've been into space buddy, and you haven't, so you'd better believe I know what I'm talking about" attitude. But the flaw I want to focus on is what can be called the argument from incredulity.

An argument from incredulity essentially works by taking the fact that one can't believe or imagine that something is true (or false) to be a good reason for thinking it isn't true (or false).

In this case, when he looks into space, Cernan simply can't believe that there isn't some kind of spiritual dimension or supreme being behind it all. And so his argument is that there is, therefore, some kind of spiritual dimension or supreme being behind it all.

And that really is the sum total of his case. He makes it sound as though you too should be equally unable to deny the deity by claiming you're not in your right mind if you do deny it. But that's just an assertion mixed up with some abuse. It doesn't advance the argument any further.

It might be thought misleading even to think of this as an argument. Rather, Cernan is merely asserting what he thinks. But there does seem to be an argument buried here, since the assertion implies that because he cannot look out into space and deny the existence of a supreme being, and he also thinks that no other sane person can either, therefore, it follows the supreme being is real. The logic of the assertion can certainly be expressed in the form of an argument without distorting what Cernan means.

Like many argumentative bad moves, once the structure of the argument is made explicit its weaknesses become obvious. Our own inability to be able to imagine that something is or is not the case is not in itself a reason to think it is or is not the case. Some true things just are unimaginable. And the fact that we have strong convictions when confronted by certain experiences does not mean that those convictions are reliable bases for true belief.

Consider just a few examples. I can't really imagine the evolution of life from single cells to human beings. But I should not think my inability to imagine this provides some kind of reason for thinking evolution is not how humans came to be. Similarly, when I see a magician saw a person in two, I can't see how the trick works. But I would be foolish to think that the person had in fact been sawn in two.

When Cernan looks out into space he can't imagine there is no supreme being and so he can't believe there is no supreme being. But he is wrong to think that his inability to imagine or believe that there is no supreme being is some kind of reason to suppose there is one. Others look out into space and do deny there is a God, and despite what Cernan says, many are in their right minds. Cernan is entitled to say no more than that he personally can't believe there is no God and accept that this only tells us about his own abilities to believe and nothing about the universe or what lies behind it.

Cernan provides a clue to the need for caution in his own words. He said there were moments when he felt he could reach out and touch the face of God. But, of course, he could never do any such thing. The fact that he felt he could is no reason to suppose he actually could; just as the fact that he felt sure God was there is no reason to suppose God was there. We should never think that what seems unbelievable to us must therefore be false, or even that what seems certain to us must be true. Our own inability or compulsion to believe is no grounds for making claims about the truth.

Julian Baggini is editor of The Philosophers' Magazine.