Soul

In the language of the poets as well as in the discourse of the philosophers, body and soul are correlative terms. Plato's Phaedo is among the earliest sustained arguments for the soul's immortality. Socrates, on the day of his execution, maintains that the true philosopher welcomes death because philosophy is "the practice of dying": the habit of turning the soul away from the body and its distractions toward the contemplation of eternal truths. If such truths are real and the soul alone can grasp them, then the soul, he argues, must be akin to the eternal. The question of whether the soul exists before joining a particular body, and after it leaves the body, is treated more fully under the idea of Immortality.

Plato's arguments for immortality are several: the cyclical recurrence of opposites, the doctrine of recollection (we remember what we knew before birth), and the affinity argument (the soul resembles what is divine and eternal). None is beyond dispute, and the interlocutors in the dialogue raise the strongest objections to them. What emerges is less a demonstration than a picture: the soul as the rational, ruling, eternal element, temporarily joined to a body that distracts and corrupts it. In the Timaeus, Plato also speaks of a world-soul, and of grades of soul in plants, animals, and men, so that the human soul is not treated only as a private principle of knowledge but as one form of animation among others.

In the Republic, Plato further elaborates the soul's structure. It has three parts (reason, spirit or thumos, and appetite), and justice is the condition in which each performs its proper function. The philosophical life is the one in which reason rules, ordering spirit and appetite toward the vision of the Good. The political analogy of the city and the soul is treated more fully under the idea of Justice; here it is enough to note that for Plato the order of the soul and the order of the state are mutually illuminating.

The problem Plato leaves open is the body itself. If the soul is more real and more self-sufficient than the body, it may be asked why it is united to a body at all, and why the body's condition affects thought, as it plainly does. Aristotle will use this question to set aside the dualist picture, arguing that soul and body cannot be treated as separable substances because the soul is the form or actuality of this particular living body.

In the opening pages of his treatise On the Soul, Aristotle says that "to attain any assured knowledge about the soul is one of the most difficult things in the world." He rejects the Platonic picture of the soul as a separable substance that merely inhabits the body. For Aristotle, the soul is the form of the living body: its organizing principle, its actuality, that which makes it the kind of living thing it is. Soul and body stand in the same relation as shape and wax, or sight and eye: the one is the form, the other its matter, and they are intelligible only together. "The soul," he writes, "cannot be without a body. Yet it cannot be a body; it is not a body, but something relative to a body."

This produces a graduated view of life. Plants have a nutritive soul, responsible for growth and reproduction; animals have a sensitive soul, adding perception, desire, and locomotion; humans have a rational soul, adding intellect. Each higher soul includes the powers of the lower. The soul is not something added to the living body but what makes the living body alive. The distinction between animate and inanimate, and among the kinds of life, is treated more fully under the ideas of Life and Death and of Mind; here the point is that "soul" for Aristotle primarily signifies the principle of life in organic bodies, not mind alone.

On the question of immortality, Aristotle is ambiguous. In De Anima Book III he distinguishes the "active intellect" (nous poiētikos), which he calls immortal and eternal. Whether this is personal immortality, whether the individual survives death, remains disputed. Where Plato holds that the soul is prior in existence to the body, Aristotle holds that soul and body come into existence together when the organism is generated. If any exception is to be made to the mortality of the soul, it is only for the human soul, because it involves the power of rational thought, which may be an activity of the soul alone.

The difficulty Aristotle leaves is the active intellect. If the soul is inseparable from this body, how can any part of it be immortal and eternal? Later interpreters will divide over this point for two millennia. Aquinas will argue that the rational soul, unlike the nutritive and sensitive souls, has an operation that does not depend on any bodily organ, and that this is why it can subsist after the body's death even though it was always the form of that body.

Marcus Aurelius represents the Stoic conception of the soul. The soul, or hegemonikon (the ruling faculty), is a fragment of divine reason, the logos that orders the cosmos, residing within each human being. To live well is to keep this inner faculty pure: free of judgments that distort, passions that enslave, and fears and desires that exhaust the self. The analogy of tyranny and slavery in the relation of the passions to reason is treated more fully under the idea of Slavery; the Stoic task is to free the soul from that bondage.

For the Stoics, the soul is material in a special sense: it is composed of the refined fire or pneuma that pervades the cosmos. But its function is governance. The rational soul can withdraw into itself, surveying externals with equanimity, recognizing that only its own judgments and choices belong to it. "Nowhere can man find a quieter or more untroubled retreat than in his own soul." On this view, the soul is not a pure immaterial substance of the Platonic or Cartesian kind, nor simply the form of an organic body in Aristotle's sense, but a corporeal yet rational principle whose excellence consists in right judgment.

On death and immortality, Marcus Aurelius is agnostic. The soul may be dissolved back into the cosmos at death; it may persist in some form; either possibility is acceptable because both are consistent with the divine order. What matters, on his account, is not the soul's survival but its condition while one lives. The Stoic task is to tend the soul as one tends a lamp: guarding its flame, removing what darkens it, keeping it upright until it is extinguished. Questions of personal survival after death are treated more fully under Immortality; here the emphasis falls on the quality of thought and conduct in the present life.

The Stoic picture bequeaths to later writers one powerful instrument and one contested premise. The instrument is the idea that the self's proper domain is its own judgments, not external circumstances. The contested premise is the soul's divinity: for Augustine, the soul is made for God but is not itself a fragment of divine reason, and without that correction the Stoic's self-sufficiency can appear as the pride that constitutes the deepest sin.

Augustine inherits the Platonic distinction of soul from body and reshapes it within a Christian account of creation and grace. The soul is immaterial, immortal, and capable of knowing eternal truths, but it is also fallen, restless, and estranged from God. "Thou hast made us for Thyself, O Lord, and our heart is restless till it rest in Thee." The inner life of the soul becomes the theater in which salvation is worked out. Unlike Socrates in the Phaedo, who tends to treat the body as the soul's prison, Augustine insists that the flesh is not evil in itself. Man is both body and soul; human nature is a thing of both flesh and spirit.

Augustine's distinctive method is introspective. In the Confessions and On the Trinity, he turns inward and finds there an image of the divine Trinity: memory, understanding, and will, three faculties in one soul. To know oneself rightly is, in some measure, to know God, because the soul is made in God's image. This gives introspection a theological weight it had not possessed in ancient philosophy. The relation of the soul's powers to knowledge and desire is treated more fully under the ideas of Mind and of Will; here the point is that self-knowledge is never merely psychological.

At the same time, Augustine insists on the soul's dependence. Its capacities are real but cannot save it. The will is free but disordered; it needs grace to love what it should love. Memory stretches back through time but requires eternity to understand itself. The rational soul is restless precisely because it is oriented toward a reality that exceeds it. Its nature is to reach beyond itself. Against those who would exalt the soul and condemn the flesh, he warns that whoever "extols the nature of the soul as the chief good, and condemns the nature of the flesh as if it were evil," is fleshly in both his love and his hatred.

When Descartes later sits alone and strips away everything uncertain, he performs a gesture Augustine had already practiced. The difference is important. Augustine's inward turn discovers a restless, dependent soul that points beyond itself to God, while Descartes' inward turn discovers the self-grounding certainty of the thinking thing, a starting point from which God becomes a conclusion rather than the precondition of self-knowledge.

Aquinas seeks to hold together two claims that had often been set against each other: Aristotle's view that the soul is the form of the body, and the Christian conviction, shared with Augustine, that the rational soul is immortal. Unlike the souls of plants and animals, which are wholly bound to matter, the rational soul has an operation (intellectual understanding) that does not depend on any bodily organ. Because a thing acts according to what it is, the rational soul must be subsistent: capable of existing on its own. "The intellectual principle which we call the mind or the intellect has an operation per se apart from the body."

Yet the soul is not naturally a complete substance by itself. It is the form of this body, and the whole human being (body and soul together) is the complete person. When the body dies, the soul persists, but in a diminished state. It retains knowledge and will but lacks the natural completion of bodily existence. For that reason resurrection is, in Aquinas's view, not an afterthought but a fitting completion: the soul's proper perfection requires reunion with a body. "If it is natural to the soul to be united to the body, it is unnatural for it to be without a body."

This account is meant to resolve a dilemma that had long troubled Christian philosophy. A purely Platonic dualism made the body's resurrection hard to understand; a strict Aristotelian hylomorphism seemed to deny personal immortality. By arguing that the rational soul is both the form of the body and a subsistent entity, Aquinas tries to preserve both the unity of the person and the possibility of life after death. He rejects the view that man is a soul using a body as a sailor uses a ship, on the ground that then man would be two substances rather than one composite nature. The status of universal concepts, on which the argument from intellectual operation partly rests, is treated more fully under the idea of Universal and Particular.

Aquinas's account became the standard synthesis of the high Middle Ages. It remains the ordinary teaching of Catholic theology on the soul and continues to attract philosophers who wish to preserve the integrity of embodiment without reducing mind to matter. The further question of the soul's destiny after death is treated under Immortality.

Descartes takes notice of the traditional ambiguities in the word "soul." When soul is identified with rational soul or thinking substance, it is usually attributed to man alone; the phenomena of life in plants and animals need not then be explained by any incorporeal principle. In his method of doubt he finds one thing he cannot doubt: that he is thinking. From the fact that, in the very act of doubting everything else, he could not doubt that he was doubting, and hence thinking, he assures himself of his existence as a thinking being. "I knew that I was a substance the whole essence or nature of which is to think," so that "this 'me,' that is to say, the soul by which I am what I am, is entirely distinct from body."

This is dualism in a sharp form. The soul and the body are two distinct substances. The soul is immaterial, indivisible, and essentially a thinking thing (res cogitans); the body belongs to the category of extended, divisible, measurable matter (res extensa). A person is the union of the two, a union Descartes struggles to explain. He suggests interaction through the pineal gland, but the deeper question remains how two radically different substances can interact at all. He also uses "soul" for the subtle fluid of the animal spirits that animate brute beasts, while insisting that this corporeal soul is not to be confused with the incorporeal mind of man. The distinction between thinking and non-thinking beings is treated more fully under the idea of Mind.

Descartes holds that the soul is even more easy to know than the body, and that even if the body were not, the soul would not cease to be what it is. From the soul's nature as a simple thinking substance, he and those who follow him (including Berkeley) conclude directly to its immortality. The argument for the soul's existence which precedes these claims is the Cogito: the soul is known first as that which thinks, not as the form of an organic body in Aristotle's sense.

Descartes sets many of the terms of modern discussion of mind and body. Subsequent writers (Hume, Kant, James, and later philosophers of consciousness) wrestle with the dualism he made vivid, whether to defend, modify, or reject it. The moral and metaphysical implications of treating animals as without thought or feeling are treated under the idea of Animal.

Hume subjects the Cartesian soul to an empiricist test. If the soul is a simple, thinking substance, then introspection should reveal it. When he looks inward, he finds no such thing. "For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception." What presents itself is not a substance underlying experience but the experiences themselves.

This is the view later called the "bundle theory." What we call the self is not a substance underlying our experiences but the collection of those experiences, bound together by memory, causation, and resemblance. The unity of the self is real in the sense that these perceptions are connected; it is not real in the sense of being the attribute of some further thing. "They are the successive perceptions only, that constitute the mind." On this account, metaphysical claims about an immortal soul-substance cannot be grounded in experience. The problem of personal identity, treated also under the idea of Mind, is recast as a problem about relations among perceptions rather than about an enduring spiritual being.

Hume is candid that this view creates difficulties. How do the perceptions hold together at all? What is doing the bundling? In an appendix to the Treatise, he confesses himself unable to solve the problem. Locke had already hesitated to convert the certainty that a thinking being exists into the assertion that an immaterial soul-substance exists; Hume goes further and dissolves even the common-sense self into a stream of impressions and ideas. The argument does not prove that no soul exists, but it does claim that experience does not warrant the traditional conception.

Hume's account is the principal empiricist alternative to Cartesian dualism among the moderns. It provokes Kant's reply in the Paralogisms, prefigures much later psychology, and remains a starting point for theories of personal identity that reduce the self to relations among mental states.

Against any form of argument for the existence and immortality of the human soul which proceeds from the nature of our thought or knowledge, Kant takes the position that the premises do not warrant the conclusion. In the "Paralogisms of Pure Reason," he claims to expose the fallacies in what he calls rational psychology. The "I" of the Cogito may be the necessary logical subject of all our judgments, but this does not give us intuitive knowledge of a really existing substance with the attributes of simplicity, spirituality, and permanence. "In all our thinking the I is the subject in which our thoughts are inherent," yet "not the slightest intuition is connected with that representation." The concept of the soul as an immaterial and simple substance may function regulatively, to guard the thinking self against materialism, but we deceive ourselves when we treat that concept as if it had intuitive content.

Against Hume, Kant insists that the unity of self-consciousness is not a mere bundle. It is the necessary form of all experience: every perception must be capable of being accompanied by "I think," or it could not be my experience at all. But this transcendental self is formal, not substantial. It is a condition of knowledge, not a knowable object. Theoretical reason cannot tell us whether there is a soul in the traditional metaphysical sense. The proposition that the soul is a simple substance "teaches us nothing at all with reference to myself as an object of experience."

Yet Kant does not abandon the soul. In the Critique of Practical Reason, he argues that the existence and immortality of the soul is a postulate or demand of the practical reason. "Of the psychic substance, regarded as an immortal soul, it is absolutely impossible to obtain any proof from a theoretical point of view," but if such an object must be thought a priori in order for pure practical reason to be used as duty commands, it becomes what Kant calls "matter of faith." Immortality seems to him rationally required as the practically necessary condition for the fulfillment of the moral law and the endless progress of the soul toward holiness of will. The relation of this postulate to duty and the highest good is treated more fully under the ideas of Duty and of Immortality.

Kant's critique reshapes the question. After him, claims about the soul can no longer rest on pure rational psychology alone; they must be grounded either in the structures of experience or in the demands of practical life. William James will later question even the practical arguments for the soul, on the ground that the concept is superfluous for scientific purposes.

William James treats the question of the soul as a question for empirical psychology. Writing as a scientific psychologist who feels "entirely free to discard the word Soul" because he finds the concept useless "so far as accounting for the actually verified facts of conscious experience goes," he agrees with Hume that introspection does not reveal a Cartesian substance. But he also observes that consciousness is not a mere bundle of discrete perceptions. It is a stream: continuous, warmly self-felt, and always selecting what to attend to. "Consciousness does not appear to itself chopped up in bits. It is nothing jointed; it flows."

James distinguishes several selves within this stream: the material self (body and possessions), the social self (how others see us), the spiritual self (inner psychological being), and the pure Ego (the "I" that thinks). The pure Ego is the felt continuity of the stream, the sense of being the same person across time. He remains agnostic about whether a metaphysical soul underlies this continuity; as an empirical psychologist, he describes what is given rather than speculating about what lies beneath. Following Locke, he does not think a substantial soul is required for personal identity and moral responsibility. The imperishability of a simple substance does not, he thinks, guarantee "immortality of a sort we care for."

This reorientation changes the traditional problem. James treats the soul first as a psychological reality rather than as a metaphysical substance. The question for him is what the actual structures of self-experience are. Consciousness, on his account, is selective and adaptive, shaped by attention and habit. He tells those who may find comfort in the idea of the soul that they are free to continue to believe in it, for his reasonings have not established the non-existence of the soul; they have only proved its superfluity for scientific purposes. The relation of consciousness to knowledge and habit is treated more fully under the idea of Mind.

James opens much of the twentieth-century discussion of consciousness. His stream metaphor enters literature, and his pragmatic psychology influences later sciences of mind. Whether the conclusion that the substantial soul explains nothing and guarantees nothing applies equally to the soul conceived as the principle of life or the form of an organic body, rather than as a spiritual agent of thought, remains a further question.

Freud replaces the traditional language of soul with that of the psyche. Where Plato gave the soul three parts (reason, spirit, and appetite) arranged hierarchically under the rule of reason, Freud describes the mind as three agencies (id, ego, and superego) locked in unstable conflict. The id is the reservoir of primal drives; the superego is the internalized voice of parents and society; the ego is the negotiator, trying to satisfy the id within the constraints imposed by reality and the superego. The analogy of bondage between the passions and reason, long present in the tradition, reappears here in clinical form.

The claim that most of mental life is unconscious is central. Consciousness is only a small portion of psychic activity; the forces shaping thought, feeling, and action often lie below the threshold of awareness. "The ego is not master in its own house." Dreams, slips, symptoms, and jokes are taken to reveal a psyche that does not transparently know itself. The Cartesian certainty of the cogito is, on this view, an illusion: we are strangers to ourselves. The problem of self-knowledge, treated more fully under the ideas of Mind and of Will, is recast as a problem of interpretation rather than of pure introspection.

This reverses much of the classical picture. For Plato, the soul becomes itself through the rule of reason. For Freud, reason is a latecomer, constantly threatened by drives it can neither extinguish nor fully understand. There is no immortal soul-substance, and no divine image in the Augustinian sense. There is the psyche: a historical product, shaped by instinct, family, and civilization, striving imperfectly for what Freud called "ordinary human unhappiness." The ethical and political bearing of this psychology is treated more fully under the ideas of Desire and of Habit.

Much twentieth-century psychology inherits Freud's deflationary picture of a mind without soul-substance or self-transparency, and without reason as simple master of the house. The inner life becomes a domain of drives, defenses, and interpretations, an object for therapy as much as for theology or metaphysics.