Involvement (Latin infinitive: involvere) plays an important and multifaceted role in Spinoza’s thought. In the opening definitions and axioms of the Ethics, Spinoza declares that the essence of a cause of itself involves its existence (E1def1) and knowledge of an effect involves knowledge of its cause (E1a4). Involvement also plays an essential role in Spinoza’s account of the finite modes in Part 2, culminating in his claims that each idea of each singular thing involves an essence of God (E2p45), and that every idea involves a volition (E2p49). Unfortunately, “involvement” is never explicitly defined by Spinoza. As Alan Gabbey (2008) has noted, “involves” normally seems to mean “implies.” For example, when Spinoza says that a cause of itself has an essence which involves existence, he means that existence follows from its essence (E1def1). Conversely, when Spinoza denies that the essence of modes involves existence (E1p24, E2a1), he means that their essence does not imply that they exist. However, there are a number of passages which complicate this story about involvement, particularly its direction and force.