The following argument is an abductive Thomistic cosmological argument from contingency, which I presented at my recent Ratio Christi debate.
- There are contingent constituents to the universe.
- Given the contingent constituents of the universe, the existence of the universe (U) is very, very unlikely under the hypothesis that these constituents are themselves uncaused or self-caused (~Cu): that is, P(U|~Cu & k) ≪ 1.
- Given the contingent constituents of the universe, the existence of the universe is not unlikely under the hypothesis of a first uncaused cause (Cu): that is, ~P(U|Cu & k) ≪ 1.
- Therefore, U strongly supports Cu over ~Cu.
The constituents of the universe include galaxies, planets, stars, cars, humans, leptons, bosons, and other particles. For the constituents of the universe to be uncaused that would mean it is metaphysically necessary. For something to be metaphysically necessary that means that it could not have failed to exist—it exists in every possible world.
For something to be self-caused it must be simultaneously antecedent to itself to produce itself as its own effect. But this contradictory. This would be akin to the ultimate bootstrapping trick.