Leibniz had a tricky philosophical mission – he was caught between Descartes and Spinoza, unhappy with the species-ism of the former, and unable to publicly advocate what he liked about the latter.  The best he could manage was Monadology, a text which has flavors of Spinozist determinism while still making a strong case for the fact that you can not have reason and still have memory, emotions, and a proper existence.  We are third-type monads, and in order to get the universe to work as it apparently does, he had to shove a lot of properties into those guys that don’t necessarily rub well together, in his honest attempt to avoid the pitfalls of Cartesian dualism.  – DvL