Leibniz associates the Principle of Contradiction and the PSR with a variety of domains where each is especially important. For example, there are domains where the truths of the domain depend on one of the two principles. These domains are characterized modally: The Principle of Contradiction rules over the domain of necessary truths and the PSR rules over the domain of contingent truths (A 6 4 1616/MP 75; G VII 355–56/LC 15–16).