Traditionally, independence accounts of substance have held pride of place. Aristotle, Aquinas, Descartes and Spinoza—among many others—accepted independence accounts in one form or another. The general thrust of such views is that substances are those things that are apt to exist in themselves. In this paper, I argue that several contemporary independence theories of substance—including those of Kit Fine, E.J. Lowe and Michael Gorman—include an ad hoc element that renders them unacceptable. I'll also consider the theories of Hoffman and Rosenkrantz.