 Leibniz presents arguments for the existence of God from the PSR in a number of different places (for example, The Ultimate Origination of Things, G VII 302–3; L 486–8. Monadology §37). Suppose that God does not exist. If God does not exist, then the only things that exist are contingent beings. Would the entire series of contingent things have an explanation? The explanation of the entire series cannot be a member of the series since then it would explain itself and no contingent thing is self-explanatory. But the explanation cannot be outside of the series because we have assumed that there is no non-contingent being, i.e., God. Thus if God did not exist, there would be something unexplained: the series of contingent beings. Everything has an explanation. Therefore God exists.