  Ancient philosophical theories of soul are in many respects sensitive to ways of speaking and thinking about the soul [psuchê] that are not specifically philosophical or theoretical. We therefore begin with what the word ‘soul’ meant to speakers of Classical Greek, and what it would have been natural to think about and associate with the soul. We then turn to various Presocratic thinkers, and to the philosophical theories that are our primary concern, those of Plato (first in the Phaedo, then in the Republic), Aristotle (in the De Anima or On the Soul), Epicurus, and the Stoics.  These are by far the most carefully worked out theories of soul in ancient philosophy.  Later theoretical developments — for instance, in the writings of Plotinus and other Platonists, as well as the Church Fathers — are best studied against the background of the classical theories, from which, in large part, they derive.