Gottfried Leibniz, who speculated that human r...

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One of the most popular family of cosmological arguments for the existence of God is based on the principle of sufficient reason. This principle dates back to at least the time of Leibniz, who used the principle to argue that contingent beings must have a sufficient reason for their existence, and that reason is God. As much as I love the cosmological argument based on neo-Aristotelian notions of cause and effect, the argument from the principle of sufficient reason fails.

Leibniz’s own argument fails, first of all, because his notion of “contingency” is only an epistemological, not a metaphysical, notion. Beings and events are contingent only from our limited human point of view. But every object and event is logically necessary given God’s preestablished harmony between the monads, the ultimate (non-spatial, non-temporal, windowless) bits of “mind-stuff” that are the basis of all being. Leibniz was such a determinist that he believed that if at time A, person B had one less hair on his head, he would literally be a different person. Thus the contingency of being is only an appearance, only a quirk of human beings’ limited capacity to know a complex world, rather than an actual state of finite beings. Leibniz’s distinction between contingent and necessary being collapses into only necessary being, and since the distinction is essential to his cosmological argument, his argument fails. A similar criticism applies to all arguments from sufficient reason that posit a necessary connection between reasons in a deductive logic framework.

A major problem with all arguments based on the principle of sufficient reason is that this principle, beloved of many rationalists, subsumes causes under reasons. But not all causes are reasons and not all reasons are causes. The cause of the late President John F. Kennedy’s death was the bullet that caused fatal brain destruction. The reasons for his death are more complex and involve the motives of Oswald, perhaps too lax security, and so forth. It is true that we talk of reasons being causes in a loose, extended sense and vice versa, but this does not imply that the distinction is illusory or unreal.

If a cosmological argument for the existence of God is to be sound, it must start from cause and effect among finite beings, with the finite causes being contingent because they do not have the cause of their existence within themselves, and therefore they are liable to change, decay, and in the case of living things, death. Aquinas’ Five Ways to prove God’s existence are examples of arguments based on traditional Aristotelian causality. Of course the arguments will have to be updated to some degree due to their statement in terms of outmoded Aristotelian science, the substance of those arguments are correct–but that discussion is for another day.