Leibniz on the PSR as a Regulative Principle of Rational Inquiry

One of Leibniz’s fundamental philosophical commitments is the principle of sufficient reason (PSR). Yet Leibniz’s precise understanding of this principle is elusive.  Leibniz provides several seemingly different formulations of its content, and Leibniz sometimes seems to require the PSR being metaphysically necessary and sometimes being metaphysically contingent.  I argue that these puzzles [...]