Pourquoi il y a plutôt quelque chose que rien?

"So far I have spoken only of what goes on in the natural world; now I must move up to the metaphysical level, by making use of a great though not very widely used principle, which says that nothing comes about without a sufficient reason; i.e. that

for any true proposition P, it is possible for someone who understands things well enough to give a sufficient reason why it the case that P rather than not-P.

Given that principle, the first question we can fairly ask is: Why is there something rather than nothing? After all, nothing is simpler and easier than something. Also, given that things have to exist, we must be able to give a reason why they have to exist as they are and not otherwise.

Now, this sufficient reason for the existence of the universe can’t be found in the series of contingent things—that is, in bodies and the representations of them in souls. I shall explain why it can’t lie in the facts about bodies; that it can’t lie in the facts about mental representations of bodies follows from that. The reason is that there is nothing in matter, considered in itself, that points to its moving or not moving, or to its moving in some particular way rather than some other. So we could never find in matter a reason for motion, let alone for any particular motion. Any matter that is moving now does so because of a previous motion, and that in turn from a still earlier one; and we can take this back as far as we like—it won’t get us anywhere, because the same question —the question Why?— will still remain. For the question to be properly, fully answered, we need a sufficient reason that has no need of any further reason— a ‘Because’ that doesn’t throw up a further ‘Why?’—and this must lie outside the series of contingent things, and must be found in a substance which is the cause of the entire series. It must be something that exists necessarily, carrying the reason for its existence within itself; only that can give us a sufficient reason at which we can stop, having no further Why?-question taking us from this being to something else. And that ultimate reason for things is what we call ‘God’." (Leibniz 1714, Principles of Nature and Grace)