The eighteenth-century German rationalist tradition is, broadly speaking, committed to (what I call) ‘the principle of rational cognition’: the grounded must be rationally cognizable from its sufficient ground. Whereas the prevailing view takes the fundamental challenge to rationalist paradise to stem from the principle of sufficient reason, I argue that it instead stems from this principle: How is it possible to rationally cognize anything at all from its ground? By investigating the opposing responses of two of Leibniz’s most influential immediate (...) successors, Christian Wolff and Christian Crusius, we find no easy way to remain in rationalist paradise. (shrink)

Leibniz's principle of sufficient reason is the claim that everything has a sufficient reason. But is Leibniz committed to the necessity or to the contingency of his great principle? I argue that Leibniz is committed to its contingency, given that he allows for the absolute possibility of entities that he claims violate the PSR. These are all cases of qualitatively indiscernible entities, such as indiscernible atoms, vacua, and bodies. However, Leibniz's commitment to the contingency of the PSR seems to stand (...) in tension with his inference of the PSR from his theory of truth. I argue that this apparent tension can be resolved satisfactorily. When it comes to his modal views on the PSR, Leibniz's position is entirely consistent. (shrink)

I examine several alleged grounds of the principle of sufficient reason in Leibniz’s philosophy. These include the nature of a requisite and a sufficient condition, the nature of truth, and the nature of harmony. I argue that Leibniz does not ground the PSR in any of these ways. Instead, he is committed to a value-based grounds of the PSR: God creates the best possible world, and the fact that the PSR obtains in this world contributes to it being the best. (...) I conclude by considering some objections to this way of grounding the PSR. (shrink)

Despite his commitment to freedom, Leibniz’ philosophy is also founded on pre-established harmony. Understanding the life of the individual as a spiritual automaton led Leibniz to refer to the puzzle of the way out of determinism as the Labyrinth of Freedom. Leibniz claimed that infinite complexity is the reason why it is impossible to prove a contingent truth. But by means of Leibniz’ calculus, it actually can be shown in a finite number of steps how to calculate a summation of (...) infinite parts. It appears that the analogy Leibniz drew between the mathematics of infinite series and the logic of contingent truths did more harm than good. A solution consistent with Leibniz’ perception of infinity is proposed. Alongside the existence of the aforementioned analogy, it is based on a disanalogy between the mathematics of infinite series and the logic of infinitely complex truths. This is a disanalogy that Leibniz had already used to solve the Labyrinth of Continuum which he declared more than once could, like the Labyrinth of Freedom, be solved by means of the nature of infinity. The solution of both labyrinths is based on the fictitiousness of the infinitesimal. (shrink)