A topic common to both Plato’s and Aristotle’s discussions of theories of the soul is the doctrine of the soul as a harmony of the parts of the body. Plato’s Phaedo as well as Aristotle’s De anima and Eudemus present this theory and argue against the identification of the soul as a harmony. This paper has two focuses, one philosophical and one historical. First, I will focus on the argumentation used by Aristotle in his dialogue Eudemus, which is often associated (...) with Aristotle’s early attachment to Plato. On the basis of the argumentation against the harmonia theory, I will try to show that the Eudemus is not a dialogue that depicts Aristotle’s Platonic phase. Instead, by comparing the arguments of the Eudemus with both Plato and Aristotle’s mature thought, I will argue that the argumentation of the Eudemus seems to be an indirect attack on Plato’s view on the Forms and on the nature of the soul, and that it seems to be consistent with Aristotle’s mature work On the Soul. Second, given that Aristotle discusses this topic twice, I will try, also on the basis of conclusions about the Eudemus and on later reception of Aristotle’s arguments, to show why this is the case. (shrink)