Contrastive PSR

In my Principle of Sufficient Reason (PSR) book, I defend a PSR that holds that every contingent truth has an explanation, but I do not defend a contrastive PSR. Many think this is a cop-out.

But it makes sense to ask why it is that

1. The moon is round and I don’t have an odd number of fingers.

The answer is, presumably, that gravity pulled the matter of the moon into a ball and I was sufficiently careful around power tools. And yet it doesn’t make sense to ask why it is that

2. The moon is round rather than my having an odd number of fingers.

This point shows that it makes no sense to have a contrastive Principle of Sufficient Reason of the following form:

3. For all contingent truths p and contingent falsehoods q, there is an explanation of why p rather than q is true.

The only time it makes sense to ask why p rather than q is true is when q is some sort of a “relevant alternative” to p. So the contrastive Principle of Sufficient Reason would have to say something like:

4. For all contingent truths p and contingent falsehoods q, if q is a relevant alternative to p, there is an explanation of why p rather than q is true.

But now note that (4) is way messier than the standard PSR, and depends on an apparently contextual constraint in terms of a “relevant alternative” which feels ill-suited to a fundamental metaphysical principle. So, I do not think a contrastive PSR just is a plausible metaphysical principle.