Wolfgang Schwarz

Modal Epistemology

Brute necessity is hard to accept, much harder than brute possibility. If someone claims that necessarily there are no purple cows, I expect an explanation. Perhaps he knows what kind of DNA is essential for cowhood and also that this kind of DNA can never produce purple beings, and he also believes that the laws of nature are necessary. This would make his claim understandable. But suppose he had no such explanation. Suppose in fact that we all know that only a minor mutation would be required to produce purple cows, a mutation perfectly compossible with the laws of nature. And still he claims that there could not be any purple cows. This would seem bizarre.

The explanation just mentioned contains another assertion of necessity: that the laws of nature are necessary. This, too, requires an explanation. That's why all proponents of the necessity of laws I know have offered quite sophisticated arguments. On the other hand, I've never seen much argument on the side of those who deny the necessity, just as no positive reason is needed to support the claim that there could be purple cows.

It's as if possibility is the default status, so that something can be treated as possible unless good reasons show that it is not. Good reasons can be largely empirical (as in the cows case) or a priori (as in the laws case). If no good reasons are forthcoming, it becomes increasingly implausible to defend the impossibility.

This suggests that all modal questions can in principle be settled by empirical research and a priori reasoning: If ideal research and resoning show a proposition to be impossible or necessary then it is so. If they don't, the proposition is contingent. Moreover, the research and reasoning does not depend on further substantial modal premises, for if it does so, as the no-purple-cows-claim depended on the no-other-laws-claim, the modal premise itself must be justified on the basis of other considerations, in this case usually semantic ones.

That looks like a nice approach to modal epistemology, because it doesn't require modal knowledge to be based on extraordinary faculties of insight into an otherworldly realm, like intuition or imagination.

To do:

• Aren't there statements of which it is at least doubtful whether they can be resolved by empirical investigation and reasoning, and not because they are vague? Examples are undecidable mathematical truths, metaphysical principles in philosophy and statements such as "there could be a world with K spacetime dimensions", with K being some cardinal for which you think the statement is very doubtful. (For most people there is such a cardinal, though which one it is varies.) The philosophical principles worry me most. The present account assumes that all questions of metaphysics, in so far they are factual at all, can be conclusively settled: the final knockdown arguments are out there, we only have to find them.
• It is not true that all necessity claims require a reason. For instance, to many it just seems obvious that Kripke is necessarily human, and that 2+2 is necessarily 4. I'm not sure, but perhaps this is not because there are no reasons but because the reasons are themselves obvious. But then what exactly are they?
• If my sketchy story deserves the name 'epistemology' it should tell us something about the justification of our modal beliefs. But it isn't clear that it does. It merely says that possibility believes are 'default justified', but what does this mean and how can it be defended? Isn't this just answering "don't worry" to the question "how do we know?"? What can we say against someone who denies that there could be people who suffer for no good reason at all, without offering a positive argument for this impossibility? It would be nice to reply that his concept of possibility is not ours because on our conception, 'possibly p' just means --- what?
• Ideally, I think modal epistemology should be treated as a subspecies of hyperintensional epistemology, and hyperintensional epistemology should be treated roughly as Stalnaker says. If we individuate the objects of knowledge ('propositions') intensionally, then there is no longer any problem of how we come to know modal propositions, for all modal propositions are necessary, and everyone trivially knows the necessary proposition. The main problem is then not modal knowledge but modal ignorance: what do we fail to know when we say that we don't know whether some modal statement p is true or false? The answer is something like: we fail to know what proposition p expresses, maybe because we don't fully understand the components of p (in particular, don't precisely know their intensions), or because even though we know them, we somehow fail to realize all the consequences of what we know.