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Leibniz and the Non-Identity Problem

Thanks to the work of the late Robert Adams, many philosophers are aware that, in his writings on the problem of evil, Leibniz anticipated Parfit's famous non-identity problem. I have not seen it noted before that Leibniz (implicitly) anticipates one of the most discussed objections to Parfit, and this is a key reason why non-identity is not a complete theodicy for Leibniz.

The non-identity problem is this. Which sperm meets which egg is an extremely chancy business, highly sensitive not just to who couples with whom, but also when and how. Ensuring that your parents meet—or even that they marry—is not nearly enough to ensure your existence. But this means that almost any action one can imagine will change which people exist in the future. And things like major economic or environmental policies, wars, and so on, are likely to result in completely different collections of people existing if not in the next generation, then at least a few generations down the line. But if this is true, then it is hard to say that such policies harm or benefit people, since those people would not have existed apart from the policies.

Leibniz holds an even more radical view about identity, sometimes called 'super-essentialism'. According to Leibniz, every fact about me is required for my being who I am. And Leibniz has an extremely broad conception of what facts are about me. For instance, 'Kenny was alive at the same time as the Russian invasion of Ukraine' is a fact about me. Thus, while it was possible for Russia never to have invaded Ukraine, the person who would have enjoyed that world would not have been me, it would've been some other guy with the same name. According to Leibniz, it follows from this that complaining about Russia's actions is really complaining against my own existence. (Leibniz says this reflection ought to stop us from complaining about the evils in the world. It's never worked for me. Your mileage may vary.)

The key result, for Leibniz, is that God does not wrong me by placing me in this world full of evils because there is no other way for me to exist. God benefits, rather than harms, me by creating me in the only circumstances in which my existence is possible.

Woodward and Hanser have both argued that Parfit's argument misses obvious ways in which we may wrong or otherwise harm people who would not have existed had we not been going to wrong them. Thus, according to Woodward, one may act wrongly by bringing a child into existence knowing that one will be severely deficient (not merely imperfect) in fulfilling one's obligations as a parent. He compares this to making a promise you know you won't be able to keep. The fact that this individual child would not have existed had you not been going to fall short of your obligations in no way relieves you of your obligations. You still wrong the child by culpably failing in them.

Similarly, both discuss an example of Parfit's, of the adoption of an economically beneficial energy policy that creates a serious risk of nuclear disaster several centuries in the future. Our actions now, in adopting the policy, would, in this scenario, cause the nuclear disaster. So we harm those future people. It doesn't matter (according to Woodward and Hanser) that those people would not have existed had the causal chain leading to the harm not already been set in motion.

Leibniz, I say, anticipates this worry because he is at some pains to argue that the case of God creating us does not have the features that worry Woodward and Hanser. Leibniz argues that God does not cause any of the evils in the world. God merely admits creatures to existence, knowing that they will cause various evils. Leibniz particularly emphasizes this point when talking about humans' wicked behavior, but for Leibniz (as can be seen, especially, in his response to William King in an appendix to Theodicy) there is no fundamental difference between natural and moral evil. Both are the product of creatures acting according to their own natures. Thus, Leibniz imagines Judas (in the Discourse on Metaphysics) or Sextus Tarquinius (at the end of Theodicy) complaining that God has given them such terrible fates. Leibniz's response is, in effect, "yes, God could have created some other Judas who was not a betrayer, but then you would not have existed. Your betrayal, like all of your actions, flows from who you are and so that other non-betraying Judas would have been another person entirely. No one but you causes your betrayal. All God does is allow you, a betrayer, to exist."

What this line of response implies is that Judas would have some grounds for complaint against God if God had somehow brought it about that Judas was a betrayer (by brainwashing or something), rather than simply bringing it about that Judas, a betrayer, exists. And this is precisely the kind of distinction that Woodward and Hanser are pointing toward in saying that we may still wrong people even if those people would not have existed if we had not been going to wrong them.

One of the things that is very helpful about Adams' work on this topic is showing how this strand of Leibniz's theodicy can be separated from his notorious optimism (his view that this is the best of all possible worlds). Leibniz apparently sees a separate problem here, that even if the universe as a whole is optimal particular creatures may have grounds for complaint of unfair treatment—or, to make anachronistic use of Kantian language, that they have been used as a mere means to the realization of the best of all possible worlds. In order to defend against this objection, Leibniz employs his radical theory of identity together with his claim that God does not cause or decree that Judas is a betrayer, but only decrees that Judas, a betrayer, exists.

This last bit shows how Leibniz can be seen as an idiosyncratic sort of neo-Thomist. (In fact, in Theodicy, he presents his own theory as a kind of synthesis of the best elements of Thomism and Molinism. In my opinion most scholars have not taken this seriously enough.) For what Leibniz makes use of is, in essence, the distinction between primary and secondary causation. Leibniz's God is not a cause among causes and therefore does not cause or bring about any of the individual evils we suffer (or commit). What Leibniz's God does do is admit us, and the world we inhabit, to existence knowing that it contains these evils. This, Leibniz maintains can be justified to each individual creature due to the fact that all of these evils are requisite for that creature's existence, and it can be justified from an impersonal perspective by the fact that the world God brings about is optimal.