Systematic metaphysics is defined by its task of solving metaphysical problems through the repeated application of single, fundamental ontology. The dominant contemporary metaphysic is that of neo-Humeanism, built on a static ontology typified by its rejection of basic causal and modal features. This book offers a radically distinct metaphysic, one that turns the status quo on its head. Starting with a foundational ontology of inherently causal properties known as 'powers', Neil E. Williams develops a metaphysic that appeals to powers in explanations of causation, persistence, laws, and modality. Powers are properties that have their causal natures internal to them: they are responsible for the effects in the world. A unique account of powers is advanced, one that understands this internal nature in terms of blueprint of potential interaction types. After the presentation of the powers ontology, Williams offers solutions to broad metaphysical puzzles, some of which take on different forms in light of the new tools that are available. The defence of the ontology comes from the virtues of metaphysic it can be used to develop. Particular attention is paid to the problems of causation and persistence, simultaneously solving them as is casts them in a new light. The resultant powers metaphysic is offered as a systematic alternative to neo-Humeanism.