...In contrast to Spinoza's view that there is only one substance, Leibniz declares that there is an infinity of substances, created and maintained in existence by god. The world that these substances compose is the best possible, created by God precisely because it is the best possible world.

...Leibniz agreed with Spinoza that everything is explicable. "There cannot," he wrote, "be any true or existent fact, or any true proposition, without there being a sufficient reason why it should be so and not otherwise" (Monadology, par. 32), and he called this the principle of sufficent reason. He differed from Spinoza, however, in that he denied that all explanation is deduction from logically necessary truths. For example, there could be laws of nature different from those that actually hold; the ones that do hold are due to the will of God. The laws of nature are indeed necessary; it does not, for example, just happen that light travels in straight lines. But they are not logically necessary, they are hypothetically necessary. That is to say, they are necessary given that such and such is the case - namely, that there is a creative deity who makes such and such decisions.