Platonic Dualism: Plato on the Soul, the Body and the Two Worlds

Platonic dualism is Plato’s view that reality comes in two very different kinds, and that one kind is higher than the other. It works at two levels. In the person, the soul is a different kind of thing from the body: invisible, not made of parts in the same way, and able to outlive the body’s death. In the world as a whole, the unchanging Forms, grasped by thought, stand above the changing things we see and touch. The soul is what we really are; the body is where we happen to be for now.

The two levels are connected, but they are not the same claim, and much confusion about “Plato’s dualism” comes from running them together. Below: the two senses, the arguments in the Phaedo, the ethical side (why the soul should rule the body), the complication of the tripartite soul, the chariot of the Phaedrus, how Plato differs from Descartes, Aristotle’s alternative, and what later thinkers made of it.

What are the two kinds of dualism in Plato?

It helps to separate them from the start.

1. Soul-body dualism (sometimes called anthropological or psychological dualism): a human being is made of a soul and a body, and the soul is the more valuable part and the true self. It can exist without the body, and did so before birth.
2. Metaphysical dualism (Forms and particulars): there is the visible world of things that come to be, change and pass away, and there is the intelligible world of Forms, which always are what they are. See Platonic idealism for this side of Plato.

The second supports the first. If there are two orders of reality, there must be something in us that can reach each one. The body, with its senses, deals with the visible. The soul, when it reasons, reaches the intelligible. Plato’s argument for the soul’s special nature leans on this match, as the Phaedo shows.

What does the Phaedo say about the soul and the body?

The Phaedo is set in prison on the day Socrates drinks the hemlock, and it is the fullest statement of soul-body dualism in Plato. (For the setting and the final scene, see the death of Socrates.) Socrates’ friends are upset that he seems so calm. His answer is that philosophers have spent their lives getting ready for this moment.

He defines death as the separation of the soul from the body, and says that those who do philosophy rightly are practising nothing else but dying and being dead (64a). The philosopher already tries, while alive, to loosen the soul’s ties to the body. So it would be absurd to be distressed when the separation finally comes (67d–e).

Why is the body a problem? The charge sheet in 65a–67b is more concrete than it sounds:

• The senses are unreliable. Sight and hearing give nothing exact, and the soul reasons best when it is least disturbed by them and keeps to itself as far as it can (65c).
• The body gets in the way. It needs feeding, it falls ill, and it fills us with desires, fears and fancies, so that it leaves us no time to think (66b–c).
• Even wars come from it. All wars are fought for money, and we need money because of the body (66c). A political point slipped into a metaphysical argument.

Later the dialogue says that philosophy finds the soul bound and glued to the body, forced to look at things through it as through the bars of a cell (82e). The prison image is strengthened elsewhere by a Greek pun Plato attributes to others: sôma (body) sounds like sêma (tomb, or sign), so the body is the soul’s tomb (Cratylus 400c, Gorgias 493a).

What is the affinity argument?

The affinity argument (Phaedo 78b–80b) is the most direct link between the two dualisms. It runs like this:

• Things that are composite can be broken up; things that are not composite cannot.
• Things that are visible change; things that are invisible stay the same.
• The body is visible, composite and changing: it is like the things of the senses.
• The soul is invisible, and when it reasons it reaches what is unchanging and is most at home there (79d): it is like the Forms.
• So the soul is akin to what is divine, deathless and indissoluble, and is likely to be indissoluble itself (80b).

Plato is honest that this shows likeness, not proof. Simmias and Cebes push back at once: Simmias suggests that the soul might be like the tuning of a lyre, which vanishes when the instrument is broken, however invisible and fine it is (85e–86d). Socrates replies, and the dialogue goes on to further arguments, but the doubt is left on the page. For all four arguments in order, see our Phaedo summary.

Why should the soul rule the body?

Platonic dualism is not only a theory about what we are made of. It is also a claim about how to live. This ethical side is what makes it so influential.

If the soul is the real self, and the body a temporary home, then caring for the soul matters more than caring for the body, its looks, its pleasures or its wealth. That is the message of Socrates’ whole career as the Apology presents it. And since the soul’s highest power is reason, the rule becomes: reason should govern the body’s desires, not the other way round. A life led by appetite is upside down. It treats the servant as the master.

In the Phaedo this sounds severe. The true philosopher takes no serious interest in the pleasures of food, drink and sex, or in fine clothes (64d–e). But the point is not hatred of the body. It is a question of priority. The body is to be looked after as far as it needs, and no further, so that it does not take over. The same idea appears in the Gorgias, where Socrates argues against Callicles that a life of ever-growing appetites is like trying to fill a leaking jar.

Does the tripartite soul complicate Plato’s dualism?

Yes, and this is the most interesting problem in Plato’s account.

In the Phaedo, the enemy of reason is the body. Desires, fears and pleasures come from it. But in Republic 4, Plato locates those same drives inside the soul. The tripartite soul has three parts: reason, spirit and appetite. The argument (439d–441c) uses conflicts we all know. A thirsty person may want to drink and at the same time hold back, so there must be one part that urges and another that forbids. The first is the appetitive part; the second is reason. A third, spirit, shows itself in anger at our own weakness, as when Leontius curses his own eyes for wanting to stare at corpses (439e–440a).

This changes the picture. The struggle is no longer simply soul against body. It is a struggle within the soul, between its better and worse parts. Justice is now reason ruling the other parts of the soul (441d–e), not a soul fleeing the body.

It also raises a hard question. The affinity argument needs the soul to be simple and without parts, since composite things can be broken up. How can a soul with three warring parts be simple? Plato seems aware of this, and he tries two answers:

1. Glaucus the sea-god (Republic 611b–612a). The soul we see is like the statue of the sea-god Glaucus, so encrusted with shells and weed that its true shape is hidden. Its real nature would appear only once it was cleaned. The lower parts would then be growths picked up from the body, not true parts.
2. The Timaeus version (69c–72d). Only reason is immortal and lives in the head. Spirit sits in the chest and appetite in the belly, and both are mortal parts made by lesser gods, which perish with the body.

Neither answer fully settles it. But both show Plato working to keep the ethical point (reason must rule) and the metaphysical point (the true soul is simple and deathless) together.

What is the chariot image in the Phaedrus?

The Phaedrus gives the best-known picture of the embodied soul. The soul is like a winged team: a charioteer and two horses (246a–b). One horse is noble and willing; the other is unruly and hard to manage. The charioteer is reason, the good horse is spirit, and the bad horse is appetite. In the gods the whole team is good; in us it is mixed, so driving is difficult.

The image blends both sides of Plato’s dualism. Before birth, souls follow the gods round the heavens and glimpse the Forms beyond them. A soul that loses its wings falls and takes on an earthly body. So embodiment is a fall away from the intelligible, which is the Phaedo’s view. But the conflict inside the team, the fight between charioteer and dark horse, is the Republic’s view: the difficulty is in the soul itself.

The Phaedrus also gives Plato’s definition of soul: it is what moves itself, and so is the source of motion for everything else (245c–e). That idea matters for the comparison with Descartes.

How is Plato’s dualism different from Descartes’?

People often treat “dualism” as meaning Descartes’ mind-body dualism and read Plato in that light. The two share a basic shape, a non-physical self distinct from the body, but they differ in almost every detail.

	Plato	Descartes
What the soul or mind is	The source of life and self-motion; it reasons but also feels desire and anger	A thinking thing (res cogitans), nothing more
What the body is	A living thing kept alive by the soul (Phaedo 105c–d)	A machine made of extended matter (res extensa) that runs by itself
Where the line falls	Between the intelligible and the sensible	Between thought and extension
Hunger and anger belong to	Parts of the soul	The body, or the union of mind and body
Why the dualism matters	Moral and religious: how to live, what happens after death	Epistemological: what can be known for certain
Before birth and after death	The soul existed before and is reborn in other lives	The mind is created by God; no rebirth
Main problem	How a simple soul can have warring parts	How two unlike substances can interact

The biggest difference is what the soul does. For Plato, soul is what makes a body alive and makes it move. For Descartes, living and moving are jobs the body does by itself, as a clock keeps time; the mind only thinks. So Descartes has a sharp “mind-body problem”: Princess Elisabeth of Bohemia asked him in 1643 how an unextended thinking thing could ever push a physical body. His answer, involving the pineal gland in the brain, satisfied few. Plato faces a version of the problem too, but he never states it so sharply, partly because his soul is already the thing that moves the body. For more on how the two thinkers differ in method, see why Plato would disagree with Descartes’ method of doubt.

What was Aristotle’s alternative?

Plato’s best student rejected the whole model. In De Anima II.1, Aristotle defines the soul as the form of a living body: the organisation that makes a body able to live, feel and think. Soul and body are related as the shape of a wax seal is related to the wax. It makes no sense to ask whether the shape and the wax are one thing or two, and so it makes no sense to ask whether soul and body are one.

On this view the soul cannot simply float off at death, any more than the shape can leave the wax. Aristotle leaves a small opening for the highest kind of intellect, which he suggests may be separable, but the Platonic picture of a self trapped in a body is gone. This is part of a wider disagreement about the Forms themselves; see Aristotle’s central critique of Plato.

How did Platonic dualism shape later thought?

It may be the Platonic idea that travelled furthest. Plotinus and the Neoplatonists made the soul’s return from the body to the intelligible world the centre of their philosophy. Through them it reached Augustine, who read the Platonists before his conversion and carried much of their picture of the soul into Christian theology.

The fit was never perfect. Christianity promises the resurrection of the body, which a strict Platonist would see as a return to prison, not a reward. That tension runs through medieval thought, and it helps explain why Thomas Aquinas later turned to Aristotle’s view of the soul as the form of the body. Still, the everyday Western picture of a person, an inner self that “has” a body the way one has a car, owes more to Plato than to anyone.

The ethical side lasted too. The idea that reason should master desire runs from the Stoics through Christian asceticism to modern ideas of self-control. Freud’s model of the mind, with its conflict between drives and a controlling ego, has often been compared with Plato’s; see Plato and Freud compared.

What are the main objections to Platonic dualism?

• The interaction problem. If the soul is not physical, how does it move the body, and how does a blow to the head affect thinking? Plato has no clearer answer than Descartes.
• The evidence from the brain. Damage to the brain changes memory, personality and reasoning. That is hard to square with a soul that does its best thinking apart from the body.
• The weak arguments. Even sympathetic readers find the Phaedo‘s arguments shaky. The affinity argument shows likeness at most, and Simmias’ lyre objection is close to the modern view that mind depends on how the body is organised.
• The ethics. Critics from Nietzsche onward have said that treating the body as a prison breeds contempt for ordinary life. Defenders reply that Plato asks for the body to be governed, not despised.
• The “ghost in the machine”. Gilbert Ryle’s 1949 phrase was aimed at Descartes, but it applies to any view that places the self in a hidden inner thing.

Few philosophers of mind today are substance dualists. Yet the questions Plato raised, whether we are more than our bodies and whether reason should rule desire, remain open. Plato’s own image for the task is the one in the allegory of the cave: turning the whole soul away from shadows and toward what is real.

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A note on quotations: translations and paraphrases are our own. For academic work, cite a standard edition using the Stephanus numbers (such as Phaedo 64a), which are the same in every translation.