  Finally, we note that there are really two distinct but related Leibnizian philosophies. The foregoing represents Leibniz’s attempt to ‘mainstream’ his thought and contribute to the broader 17th century controversy over science, epistemology, and innateness. But there is another Leibniz that we find in his more speculative, more Empedoclean, metaphysical writings, particularly the Monadology. Leibniz’ goal there is presciently like the work of contemporary string theorists – i.e., to look behind the scientific picture and lay out the still-deeper ontological and metaphysical nature of reality. The relevant point for us is that the ultimate simple elements in this system – the individual ‘monads’ – contain representations of the world beyond themselves, but these representations are not caused by the world. For Leibniz, world-to-mind causality is only an appearance. The reality is that each monad contains, as part of its essential nature, a preloaded set of representations of the world. The sequential ‘unfolding’ or ‘playing out’ of these representations can be thought of, in the case of minds, as a stream of consciousness. But the monads do not interact; instead, the streams are coordinated by a pre-established divine harmony (Leibniz’s analogy is a pair of synchronized clocks). The upshot of all this is that we arrive (again) at the radical conclusion that all thought and experience is innate. There can be no external origin for a mental element in Leibniz’s monadology, and the same can be said for the metaphysics of Spinoza, the third of the great Rationalists.