Abstract

This article analyzes one aspect of Bolzano’s metaphysics. It discusses the question of whether, according to Bolzano, substances are simple or not. In theopinion of some commentators, he accepts composed substances, that is, substances having substances as proper parts. However, it is easily possible to misinterpret his position. This paper first tries to reconstruct Bolzano’s definitions of the concept of substance and suggests that he should be able to agree with the following final definition: x is a substance if and only if x is real and not a property. After this, it is shown that, according to Bolzano, every substance is simple in a fourfold sense: No substance has (1) adherences as parts, (2) substances as proper parts, (3) spatially extended parts, and (4) temporal parts.