Abstract

I conclude that it is more accurate to say that, rather than trying to make logic metaphysical, Leibniz tries, in the context of a theistic system, to make metaphysics logical. ;I begin with a study of the principle of identity of indiscernibles, and show how it is best thought of as a principle which follows from a metaphysical interpretation of the principle of sufficient reason. It has been traditional to interpret the principle of identity of indiscernibles as primarily a merely logical principle, and thus as either trivially true, if Leibniz succeeds in proving it, or else false or contingently true. I argue that it is instead necessarily true in a non-trivial or metaphysical sense, because the principles on which it is based are themselves of this metaphysical character, contrary to what is often assumed. ;In the second chapter, I show how God's activity and a metaphysical interpretation of the principle of sufficient reason underlie Leibniz's account of space and time. ;In the third chapter, I discuss the principle of sufficient reason in detail, showing that it actually consists of three separate principles: the principle of grounds, that every true proposition has a proof a priori; the principle of reason, that God does nothing without a sufficient reason; and the principle of causation, that every event has a cause. That each of these is considered a principle of sufficient reason is explained by Leibniz's equivocal use of the term 'reason.' I show that, of the various versions of the principle of sufficient reason, only the principle of reasons provides an adequate foundation for Leibniz's principle of identity of indiscernibles and theory of space and time. Furthermore, since chapters one and two show how the activity of God is presupposed by Leibniz's metaphysics, for Leibniz to derive his metaphysics from his logic, as some would have us suppose, he would have to provide a satisfactory a priori demonstration of God's existence. But this, I argue, he cannot do. Thus God's existence and rationality, rather than subject-predicate logic, are the foundations of Leibniz's metaphysics. ;It is commonplace, when writing about Leibniz, to give primacy to his logic over his metaphysics, and indeed to try to assimilate the latter to the former. In this essay, however, I give priority to Leibniz's metaphysical pronouncements, apart, as much as possible, from logical and linguistic considerations