To explain why God is not the author of sin, despite grounding all features of the world, the early Leibniz marginalized the divine will and defined existence as harmony. These moves support each other. It is easier to nearly eliminate the divine will from creation if existence itself is something wholly intelligible, and easier to identify existence with an internal feature of the possibles if the divine will is not responsible for creation. Both moves, however, commit Leibniz to a necessitarianism that is stronger than what prominent interpreters such as Robert Sleigh and Mogens Lærke have found in the early Leibniz, and stronger than the necessitarianism that threatens his later philosophy. I defend this reading of Leibniz and propose that some features of Leibniz’s later metaphysics, including his “striving possibles” doctrine, are an artifact of the effort to rescue the early theodicy from its unwelcome implications.

This paper focuses on Leibniz’s engagement with Thomas Hobbes’s political anthropology in the Mainz-period writings, and demonstrates that Leibniz tried to construct an alternative to the English philosopher by conceiving of a physically- and ontologically-grounded psychology of actions. I provide textual evidence of this attempt, and account for Leibniz’s rejection of Hobbes’s political theory and anthropological assumptions. In doing so, I refer to diverse aspects of Leibniz’s work, thereby highlighting his aspiration to congruity and consistency between different areas of investigation. Furthermore, Leibniz’s political writings and letters will reveal another—sometimes neglected—aspect of the issue: his concern to defend and legitimize the existence of pluralist and collective constitutional political systems like the Holy Roman Empire by providing the theoretical ground of their ability to last.

In the essay “Principia Calculi rationalis” Leibniz attempts to prove the theory of the syllogism within his own logic of concepts. This task would be quite easy if one made unrestricted use of the fundamental laws discovered by Leibniz, e.g., in the “General Inquiries” of 1686. In the essays of August 1690, Leibniz had developed some similar proofs which, however, he considered as unsatisfactory because they presupposed the unproven law of contraposition: “If concept A contains concept B, then conversely Non-B contains Non-A”. The proof in “Principia Calculi rationalis” appears to reach its goal without resorting to this law. However, it contains a subtle flaw which results from failing to postulate that the ingredient concepts have to be “possible”, i.e. self-consistent. Once this flaw is corrected, it turns out that the proof – though formally valid – would not have been approved by Leibniz because, again, it rests on an unproven principle even stronger than the law of contraposition.