Bob Fischer

I contend that there are strong moral reasons for most adult family members to avoid having sex with one another; indeed, I argue that even among consenting adults, incestuous sex is usually wrong. The argument is simple. Absent compelling reasons, it's wrong to take a significant risk with something that's extremely valuable. But having sex with a family member takes a significant risk with something extremely valuable—namely, a family relationship. And since compelling reasons for taking such a risk are very hard to come by, it follows that incest is usually wrong.

Accounts of modal knowledge are many and varied. How should we choose between them? I propose that we employ inference to the best explanation, and I suggest that there are three desiderata that we should use to rank hypotheses: conservatism, simplicity, and the ability to handle disagreement. After examining these desiderata, I contend that they can’t be used to justify belief in the modal epistemology that fares best, but that they can justify our accepting it in an epistemically significant sense. Finally, I outline a modal epistemology that seems to do well by the standards I’ve recommended.