 Crusius’ attack on Wolffianism continues in his logic and his thoughts on moral philosophy. In a clear rebuke of Wolff, Crusius begins his logic by rigidly distinguishing between the methods of mathematics and philosophy, contending that where the former makes use of demonstrations that rely solely on the principle of contradiction (and relate to mere possibilities or hypothetical realities), the latter must take into account other principles when, for instance, the investigation of causes are at issue (Crusius 1747: §10). Commensurate with this, Crusius’ considerations of the traditional topics of logic—concepts, propositions, and inferences—is thoroughly informed by his account of the essence of the understanding: a philosophical inference, as opposed to a mathematical syllogism, can have as its basis what permits of being separated or combined in thought (Crusius 1747: §262). Crusius also considers the relation between philosophy and theology or revealed religion, contending for the utility of philosophy for students of theology but also arguing that religion provides a needed corrective to the misuse of philosophy which, when left to its own devices, tends to lay claim to the unrestricted use of its principles (such as PSR) whereas the appropriate restrictions are typically evident to the theologian (Crusius 1747: §32).