One of the unresolved issues in Aristotle’s hylomorphism is the part-whole puzzle. Some scholars suppose that in Metaphysics Z 17, 1041b11-33 he endorses non-mereological hylomorphism. This kind of interpretation, however, has been challenged by K. Koslicki who argues that if the evidence in Metaphysics Z 17 is combined with some related textual and conceptual considerations, then a convincing case can be made for a mereological construal of Aristotelian hylomorphism. This paper does four things. First, it scrutinizes these opposing approaches to (...) Aristotle’s theory. Second, it suggests that to adjudicate the dispute at hand one ought to determine how Aristotle deals with what has come to be known as ‘Ackrill’s problem’. It is proposed that if we consider Aristotle’s theory in light of some distinctions drawn in contemporary discussions of hylomorphism, then it transpires that he does have a solution to Ackrill’s problem. Third, it is shown that his solution to this problem suggests a particular way of settling the debate over the part-whole puzzle. And finally, it is argued that the suggested reconstruction of Aristotelian hylomorphism is consistent with the textual evidence in Metaphysics Z 17 and its associated texts. (shrink)