Koons’ epistemological argument

1. If the PSR is false, we don’t know anything empirical.
2. We know something empirical.
3. So, the PSR is true.

Inference to Best Explanation

1. Inference to Best Explanation (IBE) is a good way to reason.
2. If there is a no-explanation possibility, IBE is not a good way to reason.
3. So, there is no no-explanation possibility.

Van Inwagen against PSR

1. If p explains q, then q follows necessarily from p.
2. So, contingent truths cannot have necessary explanations. (By 1)
3. Nothing contingent explains a truth that contains it.
4. Suppose the BCCF contains all contingent truth.
5. The BCCF has no contingent explanation. (By 3)
6. The BCCF has no necessary explanation. (By 2)