Bob Fischer

A Theory-Based Epistemology of Modality

Abstract We have some justified beliefs about modal matters. A modal epistemology should explain what’s involved in our having that justification. Given that we’re realists about modality, how should we expect that explanation to go? In the first part of this essay, I suggest an answer to this question based on an analogy with games. Then, I outline a modal epistemology that fits with that answer. According to a theory-based epistemology of modality, you justifiably believe that p if (a) you justifiably believe a theory that says that p and (b) you believe p on the basis of that theory.

Modal Empiricism: Objection, Reply, Proposal

According to modal empiricism, our justification for believing possibility and necessity claims is a posteriori. One serious objection to modal empiricism is the problem of empirical conservativeness: it doesn’t seem that experience can distinguish between modal claims. If experience can’t manage that, it’s hard to see how it can provide evidence for one claim over the other. So, if modal empiricism is true, we ought to be modal skeptics. On the assumption that we shouldn’t be modal skeptics, we should reject modal empiricism. I have two aims here: first, to reply to this objection to modal empiricism; second, to sketch a modal epistemology that fits with the reply I offer.

Introduction to Modal Epistemology After Rationalism

We’re justified in believing some alethic modal claims: the losing team could have won; that bridge could collapse; two and two couldn’t equal five; etc. The epistemology of modality is concerned with the nature of this justification. How can we get it? How can we lose it? And what, exactly, explains why it’s available to us at all? The goal of this book is to give a hearing to those who are moving away from the purer strains of rationalism in modal epistemology, finding room for experience to play a larger justificatory role—or even the only role. At the same time, it makes room for those who want to construct modal epistemologies that answer primarily to ordinary modal claims rather than the ones that have been of interest to metaphysicians and philosophers of mind—e.g., teletransportation, disembodied minds, etc.

TEM and the Theoretical Virtues

This concluding chapter summarizes the case for TEM and revisits a point with which I began: namely, that TEM needn’t compete with every other modal epistemology; it can be a supplement, not a rival. To make this point clearer, I briefly discuss one essence-based modal epistemology, showing how TEM can deliver a key principle for that epistemology that might otherwise be difficult to defend.

Objections and Clarifications

This chapter replies to several objections to TEM. Among them: that physical theories can’t give us the kind of justification that TEM says they can, that TEM is circular, that TEM doesn’t fit with a standard way of arguing in metaphysics, that TEM is far too cautious about our modal justification, that TEM can’t handle conflicts between theories, and that TEM is far too permissive in terms of our modal justification.

TEM and Modal Skepticism

In this chapter, I argue that TEM is offers a better basis for modal skepticism than the one van Inwagen develops. My aim here is twofold. On the one hand, I want to show that TEM can lead to a form of modal skepticism, and if it does, then it leads to a better form than what’s previously been available. Second, I want to clarify what it would take to get a non-skeptical version of TEM—i.e., one on which we’re justified in believing some extraordinary modal claims. In other words, the goal here is to give a better sense of what TEM requires of those who think, for example, that they justifiably believe that there could be a maximally perfect being. Doing so will help us appreciate the nature of TEM’s cautiousness, as well as what’s valuable about it.

TEM’s Details

According to TEM, a person is justified in believing an interesting modal claim, p, if and only if (a) she is justified in believing a theory according to which p is true, (b) she believes p on the basis of that theory, and (c) she has no defeaters for her belief that p. Accordingly, we need a story about how we come to justifiably believe theories, a story about theories on which they have modal content, and a story about what it is to believe a claim on the basis of a theory. This chapter provides the second and third story, and explains why I can leave the problem of theory confirmation for others.