Leibniz faces a problem that many philosophers think he can’t get out of. He wants to avoid Spinoza’s view that everything is necessary, believing that God is free and has chosen the best possible world. God wouldn’t have chosen a lesser world, because God wouldn’t want a lesser world. God could have chosen not to create or to create the best possible world. Either way, Leibniz’s own Principle of Sufficient Reason requires him to say that God had to have had a reason to choose to create the best possible world rather than not create. I don’t remember enough Leibniz to know what he says about why God chose to create at all, but he does have to say this. The problem is then that it seems God had to create if there had to have been a sufficient reason to create, and he had to create this world if its being the best possible world together with God’s moral nature is sufficient for the creation of this very world. Spinozism follows, doesn’t it?
Jonathan Bennett has a nice way of putting Leibniz’s response. He says “contingency squeezes into Leibniz’s metaphysic through the narrow slit between God’s character and his actions” (A Study of Spinoza’s Ethics, p.116). Bennett thinks the problem is simply insoluble, because Leibniz wants God’s freedom to involve some sort of inclining without necessitating, something Leibniz never spells out except in terms of human choices in ways that don’t apply to God. Even if he could spell out such an account, does the Principle of Sufficient Reason allow it? Does something that inclines without necessitating still somehow a sufficient reason? Bennett says no.
I think Leibniz can be rescued from this difficulty, though I’m not sure how faithful this proposal would be to everything he says. It seems to me to be in the spirit of Leibniz.
My proposal is to distinguish between logical and metaphysical necessity and then to say that the Principle of Sufficient Reason requires a metaphysically sufficient explanation but not a logically sufficient explanation. Then Leibniz should say that God’s nature is metaphysically necessary, including his moral nature, which will guarantee him to act in a moral manner.
According to Bennett, Leibniz does say something that I can make sense of only if he thinks something like this. He says God didn’t have to act in a morally good way but did turn out to do so, and that’s why we can call God good. Leibniz also bases morality in God’s nature, thus avoiding the two horns of Socrates’ dilemma from a monotheistic revision of Plato’s Euthyphro (morality based in God’s mere choice and morality based on factors entirely outside God). Therefore, according to Bennett’s Leibniz (which I’m trusting for now) God doesn’t have to choose according to his nature. He has a morally good nature but doesn’t follow it of necessity. So Leibniz is discussing a necessary being who has a necessary nature who does things only for sufficient reasons, and yet this being doesn’t necessarily act according to his own nature? What sufficient reason would cause him to do so? This really does seem to be a problem if the same sort of necessity is at work in all these claims.
My solution makes sense of all of Leibniz’s claims. If God’s choices are metaphysically necessary given God’s necessary nature but are not logically necessary, then it seems the Principle of Sufficient Reason can be satisfied by God’s choices being metaphysically necessary. Then in his responses to necessitarianism Leibniz can say that the necessitarianism he’s avoiding is a logical necessitarianism. He doesn’t mind if everything that happens follows of metaphysical necessity from God’s nature. He does mind if everything that happens follows of logical necessity from God’s nature. God’s freedom, and thus contingency, lies in the difference between metaphysical and logical necessity. God is not forced of logical necessity to choose to create or to choose to create the best possible world. It’s logically possible that God not act according to his nature. However, it’s not metaphysically possible for God to have done otherwise, because it’s not metaphysically possible for God to act against his nature. The Principle of Sufficient Reason is satisfied if there’s a metaphysically sufficient reason for God’s actions, and there is. Problem solved.
Now all this depends on whether Leibniz could (or would want to) distinguish between metaphysical and logical necessity. He sometimes does talk in terms of logical or metaphysical vs. moral necessity, and I wonder if he could be read as really meaning logical vs. metaphysical necessity (because whatever he meant by moral necessity it doesn’t have anything to do with what people working in deontic logic mean, because that’s just having an obligation, and I’m sure Leibniz meant something stronger). So I don’t mind trying to attribute something like this to Leibniz, at least in the intent if not the way of putting it. Whether the distinction between logical and metaphysical necessity makes sense I won’t get into here. I know some people question it, and I’m not sure anyone has really formulated the distinction, but I’m equally unsure whether the objections to the distinction have any argument other than that the distinction isn’t proved.
Update: I should have mentioned that this solution came out of a conversation I had with John Hartung that started with issues completely unrelated to Leibniz. It wasn’t clear to me by the end of the conversation which one of us was more responsible for this solution to Leibniz’s problem. I can’t remember the problem John was dealing with, but this solved that too. It had something to do with Plato, Aristotle, Aquinas, and cosmological arguments, but I can’t remember what.