 c) Entailment in various Areas of Knowledge: Whenever Bolzano touches on the topic of entailment, he introduces it by examples such as those mentioned above, viz. \(\langle \sigma_1, s_1\rangle\). In these examples, what is described by \(\sigma_1\) is the cause of the phenomenon described by \(s_1\). The entailment relation is not restricted, however, to these cases where it mirrors causality of our real world on the level of propositions in World 3; for Bolzano there are also obvious examples of the entailment relation in mathematics (e.g., RW I, 160 f., WL II, 191 f., 350, 361, 368, WL IV, 34, 262 f., 448, Bolzano 1841, 106 f., Bolzano 1842, 433, Bolzano 1975, 82), ethics (e.g., WL II, 339, 348, 359, 361), metaphysics (e.g., WL II 354, WL IV, 33) and theology (e.g., RW I, 6 f., 13, WL II, 354, 361, 368). Although the majority of examples Bolzano gives for the entailment relation in WL are taken from natural sciences, he himself worked for much of his life, with great originality and success, inspired by the search for strict entailment proofs of major results in mathematics.