Julian Baggini - Do They Think Youre Stupid?

No one in their right mind could read Cernans testimony and deny that NASA must be giving its astronauts training in advanced rhetoric. In just one sentence, Cernan manages to pack three dubious, but persuasive, punches. Theres the personal, ad hominem abuse people who disagree are just not in their right mind. Theres also a whiff of the argument from authority, an Ive been into space, buddy, and you havent, so youd better believe I know what Im talking about attitude. And at the core, what can be called the argument from incredulity.

An argument from incredulity essentially works by taking the fact that one cant believe or imagine that something is true (or false) to be a good reason for thinking it isnt true (or false).

In this case, when he looks into space, Cernan simply cant believe that there isnt some kind of spiritual dimension or supreme being behind it all. The implicit argument buried beneath this assertion is that because he cannot look out into space and deny the existence of a supreme being, and no other sane person could either, therefore, it follows the supreme being is real.

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 youre not in your right mind if you do deny it. But thats just an assertion mixed up with some abuse. It doesnt advance the argument any further.

As is often the case with a bad argument, once its structure is made explicit, its weaknesses become obvious. Our own inability 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.

Even if Cernan is right about what it is possible to deny, all that would show is something about the limits of human credulity, not the existence or otherwise of things certain experiences compel us to believe.

There are plenty of examples of cases where we would be rash to make too much of our own imaginative limits. I cant 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. More obviously, when I see a magician chop a person in two, I cant see how the trick works, but I would be foolish to think that the person had in fact been sawn in half.

However, even though an argument from incredulity looks like an open and shut case of sloppy thinking, at its core is an uncomfortable truth about the fundamental limits of human reason. There always comes a point in a rational argument where you just have to see that something is the case. If Ive explained to you what numbers are, and how addition works, you just see that 1 + 1 = 2. I can explain things again if you havent got it, but at some point the truth of the sum will strike you as obvious and undeniable. Similarly, if I show you experiments that prove, say, the law of gravity, at some stage you just have to get it.