 Arnauld singled out as an example the complete concept theory of substance, which he took to imply a “more than fatal necessity” that would undermine the very possibility of human freedom. Leibniz’s attempts to forestall this implication in the sections headings of the Discours had not worked as planned, at least for Arnauld. Leibniz attempted to assuage Arnauld’s concerns in subsequent letters with moderate success.