The Argument of Time & Contingency
This argument, seen by many as strong, is quite possible in my top three arguments for the existence of God. This argument is the argument from the contingency of the world or universe to the existence of God. The argument from contingency is the most prominent form of cosmological argument historically. The classical statements of the cosmological argument in the works of Plato, of Aquinas, and of Leibniz are general statements of the modal form of the argument.
Something is “necessary” if it could not possibly have failed to exist. The laws of mathematics are often thought to be necessary. It is plausible to say that mathematical truths such as two and two making four hold irrespective of the way that the world is. Even if the world were radically different, it seems, two and two would still make four.
Something is “contingent” if it is not necessary, i.e. if it could have failed to exist. Most things seem to exist contingently. All of the humans around us might not have existed; for each one of them, whoever made it might have decided not to do so. Their existence, therefore, is contingent.
(1) Everything that exists contingently has a reason for its existence.
(2) The universe exists contingently.
(3) Therefore, The universe has a reason for its existence.
(4) Therefore, If the universe has a reason for its existence then that reason is God.
Therefore:
(5) Therefore, God exists.
Suppose that nothing has to be; that is, that nonbeing is a real possibility for everything. Then right now nothing would exist. If the universe began to exist, then all being must trace its origin to some past moment before which there existed—literally—nothing at all. But from nothing, nothing comes. So, the universe could not have begun [on its own]. But suppose the universe never began. Then, for the infinitely long duration of cosmic history, all being had the built-in possibility not to be. But if in an infinite time that possibility was never realized, then it could not have been a real possibility at all.
This hypothesis has grown in reasoning since the Guth-Vilenkin theorem was proven.