Suppose we believe that a property F is coextensive with moral permissibility. F may be, for example, the property of having the best consequences, if we are Consequentialists, or that of conforming to a universalisable maxim, if we are Kantians, and so on. This may raise the following problem. It is plausible that permissibility is “closed under implication”: any act that is implied by a permissible act must itself be permissible. Yet, in some cases, F might not be closed under (...) implication. If that is so, then F cannot be coextensive with permissibility. Maximalism has been proposed as a solution to this problem. A “maximal” act is one not implied by any other act. Maximalism restricts the claim that F is coextensive with permissibility to maximal acts only. A non-maximal act may be permissible without being F if it is implied by a maximal act that is F. The general aim of this paper is to investigate these issues by considering the formal structure of acts, or the “act-implication” relation. Discussions of Maximalism have tended to assume implicitly that acts have structure of some sort, but there has been little careful attention given to this structure. I aim to show that, by thinking about structure, we can provide a stronger defence of Maximalism. (shrink)