At this point, the contrast with Spinoza’s concept of God could hardly be starker - and that is precisely the point behind the vision. The difference goes back to that simple-sounding question: Does God have a choice? Spinoza says no; Leibniz says yes. Spinoza says that God has only one world to choose from, namely, the one that follows ineluctably from its own Nature. Leibniz counters that God always has the option not to create the world; and, when God decides to go ahead with the project, he faces a choice among an infinite number of possible worlds. Spinoza’s God has no need for anthropomorphic encumbrances such as a will or intellect, for it has no choices to contemplate and no resolutions to affirm. Leibniz’s God, on the other hand, looks much more like you or me: he must have a capacity for thought and action in order to make his choices. Finally, whereas Spinoza’s Substance is well beyond the merely human categories of good and evil, Leibniz’s God is the ultimate do-gooder, as he shuffles through all possible worlds hoping to locate “the best”.
In sum, Spinoza believes in an “immanent” God; Leibniz argues for a “transcendent” one. Spinoza’s God is the immanent cause of things: it creates the world in the same way that an essence creates its properties -that is, in the same way that the nature of a circle makes it round. It is in the world (just as the world is in it) and therefore cannot conceivably be associated with any other world or with no world at all. A transcendent God, in the other hand, is the “transitive” cause of things. He creates the world in the same way that a watchmaker makes a watch. He stands outside the world, and he would still be God whether he opted to create this world, another world, or no world at all. He has a certain degree of personhood (which is why we tend to call him “he”, in deference to the tradition). Leibniz sometimes uses the phrase “supra-mundane intelligence” to describe his transcendent God. Dropping the polysyllabes we could also say simply that Spinoza’s divinity is one that inhabits the “here and now”, while Leibniz’s resides in the “before and beyond”.
The confrontation between Leibnizian and Spinozistic conceptions of divinity, incidentally, continues to characterize discussions to the present, notably in the field of cosmology (never mind the relatively changeless field of theology). Among contemporary physicists, for example, there are those who maintain that the laws of nature are inherently arbitrary. According to their rather Leibnizian view, God (or perhaps a Great Designer) selects from among an infinite range of parameters for the laws of nature, and everything else in the world then unfolds within the chosen regime. Others physicists, however, maintain that the parameters that define the laws themselves, such that nature may account for itself in an utterly self-sufficient way. Such theorists may be said to lean to the side of Spinoza.
Taken from The Courtier and the Heretic by Matthew Stewart.