The following article is reprinted with permission from Maimonides: A Guide For Today’s Perplexed, published by Behrman House. In it, the author presents a concise summary of one of Maimonides’ proofs for God’s existence.
Having rejected a naïve understanding of God, we must ask what a sophisticated one is like. In view of Maimonides’ shift from the physical to the intellectual, we might expect that God is a necessary being with infinite knowledge and power. This expectation is borne out in the early part of Book Two of the Guide of the Perplexed, when Maimonides tries to prove that God exists. Historically, proofs of the existence of God have not played as important a role in Jewish philosophy as they have in Christian. From a Jewish perspective, it is as if a person who requires a proof to believe in God has missed the point of the religion. Still, there is no question that Judaism is committed to God’s existence, and Maimonides offers a number of arguments to show why this belief is compelling. The simplest of his arguments goes as follows.
The universe is not empty; we can at least be sure that the things we perceive with our senses exist. We can explain the existence of these things in one of three ways: (1) All things are eternal and exist necessarily, (2) Nothing is eternal and exists necessarily, (3) Some things are eternal and exist necessarily, some things not. According to Maimonides, the first explanation is obviously wrong: we see things come into existence at one moment, perish at another. The second case is also wrong. If nothing were permanent, it is conceivable that everything might perish and nothing take its place. Maimonides objects that the idea of an empty universe is absurd. So a necessary Being is needed to ensure that the universe does not become depleted.
This Being cannot derive its existence from an external source, because if it did, its existence would no longer be necessary; it would owe its existence to something else. Therefore, the necessary Being must be independent of everything else. Maimonides thinks that it is impossible for two things each to exist independently, because they would have to share a common nature or essence: independent existence. To the degree they shared it, they would be part of a larger whole and no longer independent. Maimonides therefore concludes that only one Being derives its existence from itself, and this Being is God.