An Interpretation of Leibniz's Argument from Sufficient Reason
Allegedly the deepest of all philosophical questions: Why is there something
rather than nothing?
D1: x is the world =df. x is the aggregate consisting of every contingent thing that ever did exist, does now exist, or ever will exist.
D2: x is independent of y =df. x and y are diverse and have
no parts in common.
D3: x is a sufficient reason for y =df. facts about x fully
explain why y is as it is rather than otherwise.
The Principle of Sufficient Reason (PSR): For every contingent thing, there is a some independent sufficient reason.
Leibniz suggests here that in the mind of God there are infinitely many different possible worlds, each having a chance (in some sense) at being the real world. On this interpretation, it is God, after surveying every little detail of each possible world, who decides which of these infinitely many possible worlds is the actual world, the one that really (not just possibly) exists. God, then, is the independent sufficient reason for the world.
1. The world is a contingent thing.
2. If (1), then there is some independent sufficient reason for the world.
3. If there is some independent sufficient reason for the world, then God exists.
4. Therefore, God exists. [1,2,3 MMP]
Here are some yummy rationales:
Rationale for Premise (1): To claim that the world is a contingent thing is to claim both that the world exists and that the world might not have existed.
Each person knows that the world exists because each person can reason in this way: “I know I exist and am contingent. And I know from the definition of ‘world’ that even if only one contingent thing exists, the world exists. So, I know the world exists.”
And we know that the world might not have existed because, by definition, everything in the world is contingent. If each individual thing might not have existed, it might have been that every contingent thing did not exist; in other words, it might have been that nothing existed. If no contingent thing ever existed (or will exist), then the world would not exist.
The world, then, seems contingent.
Rationale for Premise (2): This premise depends upon the plausibility of the Principle of Sufficient Reason; in fact, premise (2) is an application of the Principle of Sufficient Reason to the world via premise (1).
Rationale for Premise (3): If there is some independent sufficient reason for the world, that thing cannot be contingent. If it were, it would be part of the world and so not independent from it. Any independent sufficient reason for the world, then, must be non-contingent; it must be a necessary existent. Furthermore, anything that can fully explain why the whole world is as it is rather than otherwise must surely be powerful, and is probably knowledgeable and creative. Given all these characteristics, what else could this independent sufficient reason be, but God?