Ancient Opinions on the Soul

There were a variety of views of human nature among the ancient Greeks. Substance dualists like Plato (and later, Descartes) human beings as primarily thinking things, personal identity is grounded in the non-physical soul not in any chunk of physical matter or its arrangements. In the Platonic view then, man does not strictly speaking have a soul, but he is a soul. (Kim 2011, p. 31)  For the atomists such as Epicurus, humans were particular arrangements of atoms and to say that some particular person is the same is to say that some bunch of atoms arranged in a humanlike way are in the same kind of configuration they were in preceding days. Aristotle opposed Atomism in various places in his writings. (Thomson 2016, p. 254-5) For Heraclitus, or at least many of his interpreters, there does not seem to have been any fixed personal identity over time other than a conceptual one. Aristotle does not fall into any of these categories. Tertullian sums up these different views of humans as: 

“[T]he dignity of Plato, or the vigor of Zeno, or the equanimity of Aristotle, or the stupidity of Epicurus, or the sadness of Heraclitus.” (A Treatise on the Soul 3) 

The word “equanimity” is a good way of characterizing Aristotle’s view of human nature. It is not extreme in one direction or the other. It seeks to find a calm middle ground between the physicalism of the atomists and the dualism of his teacher Plato. There is a kind of dualism in Aristotle but it is closely fixed to the physicality of human beings. It is common, even “the standard one-line” summary to say that Aristotle viewed “the soul as the form of the living body.” (Feser 2018, p. 88.) By the “form” of the human body, Aristotle does not mean merely the shape of the human body, but a humanlike way of living, thinking, behaving and existing—primarily of thinking.  “By "form" I mean the essence of each thing, and its primary substance.” (Metaphysics 7.1032b1) For this reason he says that corpses are not really “human” because they do not perform the actions, functions, or proper ends that living humans can. They are incapable of performing the actions normally associated with humans or which are the proper end (τέλος) of humans, Aristotle explained: 

“But since it is also a body of such and such a kind, viz. having life, the body cannot be soul; the body is the subject or matter, not what is attributed to it. Hence the soul must be a substance in the sense of the form of a natural body having life potentially within it.” (De Anima 2.1.4.)

The body is not identical to the soul, but the soul inheres in the body because it is a term which describes the life of the body, or rather, the kind of life it has, as he says: 

“[T]he soul of animals (which is the substance of the living creature) is their substance in accordance with the formula, and the form and essence of that particular kind of body (at least each part, if it is to be properly defined, will not be defined apart from its function; and this will not belong to it apart from perception.” (Metaphysics 7.1035b8-9) 

For Aristotle there are two parts of the rational soul, the human soul, are the scientific (ἐπιστήμη) and deliberative (νοῦς). Practical knowledge is primarily a feature of the former. Plato believed that human beings had an innate knowledge of the form of the Good. (Republic 505a-514a) Plato taught that our souls pre-existed our births, and resided in the world of the forms. (Phaedo 72e-28b) When our souls became incarnate in human bodies, they retained a kind of innate but hazy knowledge of the forms. By introspection human beings were able to recall the knowledge of the form of the good, so in a sense, this is practice for death, which is a return to a disembodied state. (Phaedo 59c) Aristotle takes quite the reverse approach and emphasizes the influence of the external world on our inward character. Aristotle teaches that things have purposes or “final causes” (αιτία) inherent within themselves. (Physics 2.2) The unique and primary function of humans is to be rational and reasonable. This is the purpose or final cause of humans. Human beings are meant to live, so corpses do not strictly speaking have a human “form.” (Metaphysics 7.1035b) For this reason, Aristotle says the ideal life which is the good life (εὐδαιμονία) means  to live a rational life while having physical needs satisfied. 

For Epictetus, it is possible to have a good life (εὐδαιμονία) even while suffering physical trials or losses by remaining indifferent to “things which are not in our control.” (Enchiridion 1, 14) If one remains indifferent to loss and understands that things outside of their power should be beyond their concern, happiness may be found even without external goods. But for Aristotle, expression of reason and the enjoyment of physical or external goods are both necessary for a good life. So it is possible that bad fortune, such as poverty or some other misfortune can cause a virtuous person to miss out on εὐδαιμονία. In other words, attaining a virtuous character is only part of what it means to have εὐδαιμονία in Aristotle but for the stoics it is everything.