The paper proposes a formal account of Aristotle's trichotomy of verbs, in terms of properties of their continuous tensings, into S(state)-verbs, K(kinesis)-verbs, and E-(energeia)-verbs. Within a Fregean tense framework in which predicates are relativized to times, an account of the continuous tenses is presented and a preliminary account of the trichotomy devised, which permits an illuminating analogy to be drawn between the temporal properties of E- and K-verbs and the spatial properties of stuffs and substances. This analogy is drawn upon (...) in constructing a sophisticated version of the preliminary theory accommodating more of the linguistic data. (shrink)