Abstract
This is a review essay on Daisuke Kachi’s recent book, Agents: Contemporary Substance Ontology (sic. Shunjusha, 2018). The book develops and partially defends an ontology that takes the category of substance as the most fundamental one. The author provides in it a new perspective on substance, which consists in characterizing substances as bearers of what he calls “substance modalities” (of which there are four kinds, that stem from the factors of essence, power, past persistence, and future persistence respectively). The first part of this review essay gives an extended overview of Kachi’s book while the second discusses some problems it may face.