Aristotle was a student of Plato’s at The Academy in Athens, and it was there that Aristotle’s beliefs diverged from those of his tutor. This distinction in beliefs is famously depicted by Raphael’s painting Scuola di Atene. Plato, who is often regarded as the founder of Western Philosophy, is shown pointing upwards, demonstrating the precedence he places on a priori reasoning and the metaphysical, whereas Aristotle’s hand faces the ground, showing his reliance on empiricism and the knowledge one can gain from the natural world. Plato believed in two distinct worlds: our world, the world of appearances, and the world of the forms. Aristotle, on the other hand, saw our world and our lives as final, not believing in an afterlife or any distinct realm. Although Aristotle believed in a supernatural Prime Mover, this being had no direct interaction with our world and gave no evidence for a life beyond death. Thus Aristotle was much more concerned with the world around us and what we can learn from it, while Plato believed more in the metaphysical; this perhaps explains their differing views on the soul’s mortality.
Plato and Aristotle were both dualists in that they both believed that we have two elements, a body and a soul. Their ideas largely stem from beliefs passed down by pre-Socratic thinkers living in Greece. Pythagoras and Homer both had a huge influence on Plato’s theory of the soul, particularly on his beliefs about the soul’s immortality. In Homer’s The Iliad and The Odyssey characters visit the underworld and meet the souls of those who have died. Thus for Homer, and indeed for many Greek thinkers, the soul is what endures in the underworld after death. The fact that certain souls are recognisable to characters like Odysseus who venture down to the underworld suggests that a person’s identity and personality are to be found in the soul. Pythagoras also believed that the personality was a part of the soul, and indeed that the soul was immortal and continued after death. However for Pythagoras the soul did not simply remain in the underworld; rather it entered other bodies and continued living as the same person but in another form, whether that form is of a human or a plant.
Plato drew on these beliefs and concluded that the human soul is eternal. He also referred to the human person as a soul imprisoned in a body, explaining his belief that the soul is an entirely separate and independent entity. Plato attempted to support these claims in his work the Phaedo. He presents four different arguments for the souls existence. The first argument, the Argument from Opposites, observes that everything comes to be from out of its opposite. Therefore, since life and death are opposites one can reason analogously that, just as the living become dead, so the dead must become living; thus the soul must be immortal. His second argument, the Theory of Recollection, states that learning is simply a process of recollecting things one knows before birth. This would therefore suggest that the soul exists before birth (to see the Forms), and so is eternal. The most notable argument, the Argument from Affinity, distinguishes between two types of things: things which can be destroyed (material objects), and things which cannot be destroyed (non-perceptible, intelligible things, like the Forms). Since the soul is intelligible but not perceptible, it must also be indestructible, and thus eternal. Finally, the Argument from the Form of Life argues that all things participate in their Forms (e.g. beautiful things participate in the Form of beauty), and since the soul, by its very nature, participates in the Form of Life, it must be eternal. For these reasons, largely based on his Theory of the Forms, Plato is adamant that the soul is immortal.
Aristotle, however, viewed the soul very differently, presenting his views in his work De Anima. Although he was a dualist, he did not see the soul as completely independent from the body. Rather, for Aristotle the soul could not exist without a body to animate. Heraclitus, the Greek philosopher known for his aphorism “You could not step twice into the same river”, also believed that the soul is what animates the body. The soul, for Heraclitus, was linked to the body and is part of it, rather than being completely distinct. He said that because we need the body and senses to gain knowledge, so the soul and the body must be connected. Aristotle, who referred to the soul as the ‘anima’, saw the soul as very similar to the mind in that it is the difference between a living body and a dead corpse. The body and soul are separate, but cannot be separated. For him, the soul is the “cause and principle of the living body”. Aristotle also saw the soul as the imprint or recognisability of the body; for instance, he says that if the eye were a body, its soul would be its capacity to see. Thus he did not believe that the soul is eternal; however, his thoughts are rather inconsistent, since he does suggest that intellectual thought continues after death.
Both philosophers, as well as disagreeing over the mortality of the soul, also disagreed over the characteristics of the soul. Plato maintained that the soul is rational and that it is affected negatively by material things (or, as he says, when it “attends to perceptibles”). The soul works with the mind to overcome this dizziness. In order to explain his beliefs about the soul, Plato used the Chariot Analogy: he said that the soul was a chariot driver driving two horses, the mind and the body. These horses pull in different directions. It is the soul’s job to control them and ensure that they work in harmony. The ultimate goal for the soul is to achieve harmony and thus gain knowledge of the World of the Forms. However, the body distracts the soul from this goal:
“The body is the source of endless trouble to us by reason of the mere requirement for food… It fills us full of loves, and lusts, and fears, and fancies of all kinds, and endless foolery, and in fact, as men say, takes away all power of thinking.” – Plato, Phaedo
In the Republic Plato divides the soul up into three parts, and this belief is known as Plato’s Tripartite Theory of the Soul. He said that the soul was composed of spirit, reason and appetite. Reason is in charge, and it is the part that guides and regulates, working through the mediums of logic and knowledge. Spirit is (more often than not) an ally of reason and controls how we are seen: it is concerned with emotions, honour, motivation, self-assertion and ambition, amongst other things. Appetite is the part of the soul that gives rise to our desires whether they are necessary, unnecessary or perverted. Plato says that sin and crime stem from disharmony of these three parts (i.e. when desire overpowers reason). Whereas in the Phaedo Plato insists that the soul and mind are completely separate, and also that desires are caused by the body not the soul (demonstrated by the chariot analogy), in the Republic he claims that desires too come from the soul, as does reason. Thus his theory of the soul is incomplete and contradictory.
Aristotle, on the other hand, divided the soul into two main parts, and four sub-parts. The two main parts are the Rational (containing the Calculative and Scientific parts) and the Irrational (containing the Desiderative and Vegetative parts). The Calculative part of the soul is the part that is relied on for balancing and weighing up options when decision-making; the Scientific part, on the other hand, searches for a priori truths. The Desiderative part is concerned with what one wants to do, and the Vegetative section is concerned with basic desires (e.g. the desires for food or sex). To function correctly, the soul must be balanced, and true virtue can only be achieved when the soul functions properly. Finally, Aristotle outlined the different faculties of the soul. He believed that there is a hierarchy of faculties, including nutrition, perception, desire, locomotion and intellect. Not all animals have each faculty – it is the faculty of intellect that distinguishes humans from other animals.
For both Plato and Aristotle it is up to the soul to control emotions and desires to ensure harmony. In fact, the idea of balancing desires and controlling emotions is a central part of Aristotle’s Virtue Ethics. When desires are not efficiently controlled, this is known as ‘akrasia’ (a weakening of the will). Despite the similarity of the two men’s beliefs concerning desires and reason within the soul, their beliefs differ dramatically about the soul’s mortality and its characteristics.