Hylomorphism is a metaphysical theory that explains the unity of material objects through a special immaterial part, a ‘form’. While contemporary accounts of hylomorphism appeal to structure, and advocate that material substances can have other substances as parts, James Dominic Rooney highlights the flaws in this Neo-Aristotelian way of thinking. Instead, he draws on medieval European and Chinese traditions to put forward that the classical approach to the unity of material objects in terms of ‘form’ remains theoretically superior. Rooney shows how Thomas Aquinas’ account of...