Implicative verbs (e.g. "manage") entail their compliment clauses, while non-implicative verbs (e.g. "want") do not. For example, while "managing to solve the problem" entails "solving the problem", no such inference follows from "wanting to solve the problem." Differentiating between implicative and non-implicative verbs is therefore an essential component of natural language understanding, relevant to applications such as textual entailment and summarization. We present a simple method for predicting implicativeness which exploits known constraints on the tense of implicative verbs and their compliments. We show that this yields an effective, data-driven way of capturing this nuanced property in verbs.