At least since Robert Cummins’s paper “Reflections on Reflective Equilibrium”:http://books.google.com/books?id=kOjtQwQ0XmkC&pg=PA113&source=gbs_toc_r&cad=0_0&sig=ACfU3U3tRJ9Pv34k2FDeD3emET6VzxcK2g in “Rethinking Intuition”:http://books.google.com/books?id=kOjtQwQ0XmkC, a lot of people have worried that intuition, that old staple of philosophical argument, is unreliable. This is fairly important to the epistemology of philosophy, especially to intuition-based epistemologies of philosophy, so I think it’s worth considering.

(Worries about intuition obviously don’t start 10 years ago, but the particular worry about reliability does become pronounced in Cummins. I suspect, though I don’t have the relevant papers in front of me, that there are related worries in earlier work by Stich. Note that this post is strictly about reliability, not a general defence of intuition in philosophy.)

The happy new is that there’s a simple argument that intuition isn’t unreliable. I think it isn’t clear whether intuition simply is reliable, or whether there’s no fact of the matter about how reliable it is. (Or, perhaps, that there is no such thing as intuition.) But we can be sure that it is not unreliable.

Start with a fact that may point towards the unreliability of intuitions. Some truths are counter-intuitive. That’s to say, intuition suggests the opposite of the truth. I’m told it’s true that eating celery takes more calories than there is in the celery, so you can’t gain weight by eating it. If true, that’s pretty counterintuitive. And just about everything about “counter-steering”:http://en.wikipedia.org/wiki/Countersteering strikes me as counterintuitive. So those are some poor marks against intuition.

But now think of all the falsehoods that would be even more counterintuitive if true. If you couldn’t gain weight by eating steak, that would be really counterintuitive. Intuitively, steak eating is bad for your waistline. And that’s true! Intuitively, you have less control of a motorbike at very high speeds than at moderate speeds. And that’s true too! It would be really counterintuitive if remains from older civilisations were generally closer to the surface and easier to find than remains from more recent civilisations. And that’s false – the counterintuitive claim is false here.

In fact almost everywhere you look, from archeology to zoology, you can find falsehoods that would be very counterintuitive if true. That’s to say, intuition strongly supports the falsehood of these actual falsehood. That’s to say, intuition gets these right.

To be sure, most of these cases are boring. That’s because, to repeat a familiar point, we’re less interested in cases where common sense is correct. And here intuition overlaps common sense. But that doesn’t mean intuition is unreliable; it’s just that we don’t care about it’s great successes.

There are so many of these successes, so many falsehoods that would be extremely counterintuitive if true, that intuition can hardly be unreliable. But maybe it’s not actually reliable either. I can think of two reasons why we might think that.

First, there may be no fact of the matter about how reliable intuition is.

It’s counterintuitive that there can be proper subsets of a set that are equinumerous with that set. And that’s true, so bad news for intuition. It would be really counterintuitive if there could be proper subsets of a set of cardinality 7 that are also of cardinality 7. But there can’t be, so good news for intuition. And the same for cardinality 8, 9, etc. So there are infinitely many successes for intuition! A similar trick can probably be used to find infinitely many failures. So there’s no such thing as the ratio of successes to failure, so no such thing as how reliable intuition is.

On the other hand, perhaps we’re counting wrongly. Perhaps there is one intuition that covers all of these cases. Perhaps, though it isn’t clear. It isn’t clear, that is, how to individuate intuitions. Arguably our concept of an intuition isn’t that precise to give clean rules about individuation. But if that’s right, there again won’t be any fact of the matter about how reliable intuition is.

This isn’t, I think, bad news for using intuition in philosophy. Similar arguments can be used to suggest there is no fact of the matter in how reliable vision is, or memory is. But it would be absurd on this ground to say that vision, or memory, is epistemologically suspect. So this doesn’t make intuition epistemologically suspect.

Second, there might be no single such thing as intuition. (I’m indebted here to conversations with Jonathan Schaffer, though I’m not sure he’d endorse anything as simple-minded as any of the sides presented below.)

It would be counterintuitive if steak eating didn’t lead to weight gain. It would be counterintuitive if Gettiered subjects have knowledge. In both cases intuition seems to be correct. But perhaps this is just a play on words. Perhaps there is no psychologically or epistemologically interesting state that is common to this view about steak and this view about knowledge.

If that’s so, then perhaps, just perhaps, one of the states in question will be unreliable.

I doubt that will turn out to be the case though. Even if there are distinct states, it will still turn out that each of them gets a lot of easy successes. Let’s just restrict our attention to philosophical intuition. We’ll still get the same results as above.

It would be counterintuitive if torturing babies for fun and profit was morally required. And, as it turns out, torturing babies for fun and profit is not morally required. Score one for intution! It would be counterintuitive if I knew a lot about civilisations on causally isolated planets. And I don’t know a lot about civilisations on causally isolated planets. Score two for intuition! It would be counterintuitive if it were metaphysically impossible for me to put off serious work by writing blog posts. And it is metaphysically possible for me to put off serious work by writing blog posts. 3-0, intuition! I think we can keep running up the score this way quite easily, even if we restrict our attention to philosophy.

The real worry, and this might be a worry for the epistemological significance of intuition, is that the individuation of state types here is too fuzzy to ground any epistemological theory. For once any kind of intuition (philosophical, epistemological, moral, etc) is isolated, it should be clear that it has too many successes to possibly be unreliable.