Hervaeus Natalis on Astral Determinism and the Contingency of Sublunary Effects

This article examines Hervaeus Natalis’s rejection of astral determinism, that is, the thesis that the movements of heavenly bodies make all sublunary effects necessary. Hervaeus develops his anti-deterministic arguments in two key texts: Scriptum super iv libros Sententiarum (Book ii , d. 15, q. 1, a. 4) and De materia caeli , q. 9. He argues that celestial causes do not act with absolute necessity, since they can be impeded by external factors such as the action of a contrary agent and the indisposition of sublunary matter. Hervaeus further seeks to ground the contingency of sublunary effects in a notion of causal indeterminacy. The Scriptum attributes this indeterminacy to the unlimited ways in which sublunary matter can be disposed, while the De materia caeli appeals to the indeterminacy of accidental factors that may prevent or promote the occurrence of those effects. The article addresses the difficulties faced by both accounts.