Notes on Peter van Inwagen's Criticisms of the Cosmological Argument in Metaphysics
1. Two versions of PSR:
1.1 Unrestricted PSR: For every object and state of affairs, there is a sufficient reason for why it exists or obtains
1.2 Restricted PSR: For every object, there is a sufficient reason for why that object exists
2. Problems for PSR
2.1 Unrestricted PSR is absurd
2.1.1 If Unrestricted PSR is true, then every fact of the universe had to obtain of logical necessity (for the details, see van Inwagen's chapter on the cosmological argument in his Metaphysics)
2.1.2 But that's absurd: some events are surely logically contingent (e.g., my typing this post).
2.1.3 So, not-Unrestricted PSR
2.2 Restricted PSR is plausible, but it won’t help in demonstrating that there is a necessary being
2.2.1 If Restricted PSR is true, it doesn’t have the absurd consequence that every fact in the universe had to obtain of necessity
2.2.2 However, we can only use Restricted PSR to demonstrate that a necessary being exists only if the universe as a whole is an individual object.
2.2.3 But the universe can’t plausibly be taken to be an individual object
2.2.4 Rather, the only plausible way to think of the universe is that of an enormous collection of objects (See PvI's book, Material Beings, for the details of the argument here).
2.2.5 But if so, then perhaps there are infinitely many objects in the universe, stretching through a beginningless past, and the existence of each member of the collection can be explained in terms of one or more other members of the collection.
2.2.6 And if so, then we need not posit a necessary being to explain the existence of the universe.
2.3 Therefore, on either version of PSR, the Leibnizian cosmological argument fails.