Abstract
In a difficult but fascinating passage in Metaphysics Z.17, Aristotle puts forward a proposal, by means of a regress argument, according to which a whole or matter/form-compound is one or unified, in contrast to a heap, due to the presence of form or essence. This proposal gives rise to two central questions: (i) the question of whether form itself is to be viewed, literally and strictly speaking, as part of the matter/form-compound; and (ii) the question of whether form is to be regarded as itself having parts. It is argued that both questions may be answered affirmatively, without giving rise to a regress worry.