The Aristotelian account of change—according to which no individual can survive a change of species because an individual's essence is, at least in part, determined by its species membership—remains popular in the seventeenth century. One important, but often overlooked dissenting voice comes from Anne Conway. Unlike many of her contemporaries, Conway firmly rejects the Aristotelian account of change. She instead endorses the doctrine of Radical Mutability, the view that a creature can belong to different species at different times. A horse, for example, can gradually become a human being and yet remain the same individual. Why, though, is Conway so opposed to the prima facie appealing Aristotelian account of change? This paper claims that she levels two arguments against this account which have been largely neglected so far. First, she argues that there could be no causal interaction between creatures belonging to different species with distinct essences, because cause and effect would be too dissimilar in that case. Second, Conway argues that the Aristotelian model is inconsistent with divine goodness because it allows for the annihilation of creatures and because it imposes arbitrary restrictions on the capacity of creatures to improve.