Mind

Mind, which Plato calls nous, is a part or power of the soul, distinguished from sense and imagination as well as from appetite and the passions. What the senses report belongs to the world of becoming, and what they yield is opinion rather than knowledge. Mind alone apprehends the Forms, those unchanging intelligible realities such as Justice Itself or Beauty Itself, and through them the Good, which the Republic compares to the sun as at once the source of the being of intelligible things and the cause of the mind's power to see them.

The divided line and the figure of the cave in Books VI and VII set out degrees of knowing rather than a simple opposition of sense and intellect. Imagining and belief occupy the lower segments, mathematical reasoning and dialectic the higher, and the ascent from one to another is described as a turning of the whole soul rather than the insertion of sight into blind eyes. Since reason is the part fit to rule, the right ordering of the soul and the right ordering of the city are treated by Plato as versions of a single question, a matter taken up more fully under the ideas of Justice and the State.

The Meno and the Phaedo account for the mind's possession of such objects by the doctrine of recollection. Learning, on this view, is not the reception of something from without but the recovery of what the soul beheld before birth, and the questioning of the slave boy in the Meno is offered as evidence that the truths of geometry can be elicited rather than taught. The mind is thus akin to its objects, and it is by sharing their eternity that it is able to know them. Whether the senses merely remind, or instead supply materials from which universals are abstracted, is among the points on which Aristotle and Aquinas afterwards depart from Plato.

The Theaetetus proceeds in the opposite direction, examining in turn the proposals that knowledge is perception, that it is true opinion, and that it is true opinion together with an account, and finding each defective. The dialogue leaves the question open, but in the course of it Plato marks the ways in which mind may be confused with sense, with belief, or with the mere naming of things. The tradition receives from him both a doctrine of the mind's affinity with eternal being and an analysis of its liability to error.

The Platonic conception of mind as the soul's highest part, divine in origin and most itself when turned from the senses toward the intelligible, sets the terms of much that follows. Aristotle retains the distinction between sense and intellect while rejecting recollection; Augustine takes over the doctrine that the soul somehow possesses truths it did not acquire, and locates their source in divine illumination rather than in a former life. The question whether the objects of the mind exist apart from minds and from sensible things is pursued further under the ideas of Idea and Form.

Aristotle retains the distinction between sense and intellect while rejecting the doctrine of recollection. In the De Anima the soul is defined as the form of a living body, and mind, or nous, as that power of the soul whereby it thinks and judges. Mind is said to be "in a way all things," since it is capable of receiving the intelligible form of anything whatever; before it thinks it is none of them, and in thinking it takes on the form of its object without the matter. It is therefore unmixed and without an organ of its own, for a power that is to receive all forms can have none of them antecedently.

In the third book a distinction is drawn between an intellect which becomes all things and an intellect which makes all things, as light makes potential colors actual. The former is variously called the passive or possible intellect, the latter the active or agent intellect, and of the active intellect Aristotle says that it is separable, impassible, and alone immortal. The passage is brief and its meaning contested, and the several ways of taking it divide the commentators, as does the further question whether the intellect so described belongs to each man individually or is somehow one for all.

The operations assigned to the intellect are more fully set out elsewhere. Nothing is in the intellect that was not first in sense; the mind works upon images furnished by the sensitive part, abstracting from them what is universal, and then proceeds to form propositions out of concepts and to see how one proposition follows from another in inference or demonstration. Understanding, judgment, and reasoning are thus three acts of a single power rather than three powers. The Ethics adds that the exercise of this power in contemplation is the activity in which human happiness is most completely realized, a claim treated more fully under the ideas of Happiness and Wisdom.

The doctrine of the active intellect occupies the commentators for centuries. Alexander of Aphrodisias identifies it with something outside the individual man, while Aquinas takes both intellects to be powers of each human soul, and the Averroist reading, that the intellect is numerically one for the whole species, is disputed at length in the schools. What is at issue in these readings is whether what thinks in a man is properly his own, and the bearing of that question on personal survival is considered under the ideas of Soul and Immortality.

Augustine turns the examination of mind inward and finds there an image of God. In On the Trinity he argues that the human mind, or mens, reflects the triune God in a threefold unity of memory, understanding, and will, which may also be described as the mind, its knowledge of itself, and its love of itself. These are not three things but one mind in three acts, distinct in what they do yet inseparable in their being, each of them in some manner containing the others. The analogy is offered as an image and not as a demonstration, and Augustine repeatedly notes how far the likeness falls short of what it is a likeness of.

In distinguishing understanding from will as separate faculties of the soul, Augustine departs from Plato and Aristotle alike, who tend to treat knowing and loving as diverse aspects of a single mental life. Aquinas afterwards follows him on this point while following Aristotle on the acquisition of ideas. The bearing of the distinction is considerable, since it makes the assent of the mind to what it does not see, and the direction of the mind by love toward what it seeks to see, into acts of different powers. These matters are pursued further under the ideas of Will and Love.

The tenth book of the Confessions traces the structure in experience. The "vast court" of memory holds not only the images of things perceived but the self's own past, its notion of God, and the rules of truth which the mind did not make and cannot alter. The mind is in this respect greater than itself, since it does not comprehend the whole of what it contains. Augustine adds an argument against the Academic skeptics: whoever doubts knows that he doubts, and if he is deceived, he exists. The mind's presence to itself is thus immediate and cannot be argued away, though for Augustine the certainty so gained points beyond the mind to the unchanging light by which it judges.

What Augustine bequeaths to the later tradition is the practice of taking the mind's knowledge of itself as a starting point rather than a result. Descartes makes a comparable move without the Trinitarian setting, and the resemblance between the two arguments has often been remarked, as have their differences of purpose. Whether the self-certainty in question terminates in the thinking subject or leads on to the divine illumination Augustine supposed is a question that belongs as much to the chapters on God and Knowledge as to this one.

Aquinas draws together the Aristotelian and Augustinian accounts into the most fully articulated medieval theory of mind. The intellect is a power of the soul, not the soul itself, and its proper object is being as intelligible. Since the forms of things are not actually intelligible as they exist in matter, Aquinas argues that two intellectual powers must be posited: an agent intellect, which makes things actually intelligible by abstracting the species from material conditions, and a possible intellect, which receives the species so abstracted and is thereby brought from potency to act. Nothing, he observes, is reduced from potentiality to act except by something already in act.

The possible intellect may accordingly be considered in three states: in complete potentiality, before it has come to understand a given thing; in habitual possession of what it has understood but is not now considering; and in act, when it actually exercises that habit. Upon the reception of the species the intellect performs three operations, forming concepts, joining and dividing them in judgment, and passing from one proposition to another in reasoning. Aquinas holds that these operations do not require distinct powers, and he says the same of the speculative and practical intellect, which differ only in their ends, the one directing what it apprehends to the consideration of truth and the other to action.

Against those who would place the mind's objects outside the sensible world, Aquinas maintains that in this life knowledge begins with the senses; against those who would make the mind corporeal, he maintains that a power which receives forms universally can be the act of no bodily organ. The human soul is the form of the body and yet has an operation in which corporeal matter has no share. The body remains necessary to the act of understanding, not as its organ but on the part of the object, since the intellect must turn to the images the sensitive powers supply. Where imagination or memory is impaired, as in frenzy or lethargy, a man is hindered from understanding even what he formerly knew. Self-knowledge is on this account indirect, the mind coming to know itself through its acts of knowing other things.

The synthesis holds together only so long as abstraction is granted. Descartes dispenses with it by identifying the mind with the thinking substance itself and treating its principal ideas as innate; Hobbes dispenses with it by denying that there are universals to be abstracted, allowing only universal names. The immateriality of the intellect, and the difficulties it raises for the union of soul and body, are treated at greater length under the ideas of Matter and Soul, while the doctrine of intelligences wholly separate from matter belongs to the chapter on Angel.

Descartes differs from all the writers so far considered in identifying the human mind with the rational soul of man. The two are not related as power to substance, nor is thinking an act which the soul sometimes performs and sometimes omits. Thought is the very essence of the soul, as extension is the essence of body, and just as a body cannot exist without having three dimensions, so on this view the mind cannot exist without thinking. The phrases "rational soul" and "mind" are used interchangeably throughout his writings, and the faculties which earlier authors distributed among distinct parts of the soul are treated instead as acts of the one thinking thing.

The argument of the Second Meditation proceeds from doubt. Whatever can be doubted is set aside, and what remains is that the doubter exists so long as he thinks. The cogito may be rendered as "thinking is, therefore the mind is," or equivalently as "the mind exists, therefore there is thinking," and it is this equation of the mind's existence with the activity of thought that Locke afterwards disputes. In the dual nature of man there are accordingly two substances, a res cogitans whose activities are understanding, willing, imagining, and feeling, and a res extensa whose activities are magnitude, figure, and motion, the two having, in Descartes' phrase, no affinity with one another.

From this real distinction the modern problem of the union of mind and body arises. Descartes affirms that the two interact and locates the point of their commerce in the pineal gland, and the Passions of the Soul undertakes to describe how the motions of the animal spirits give rise to the passions and are in turn governed by the will; but the manner of the interaction remains obscure, and later writers, Locke and Hume among them, confess as much. The same separation leads Descartes to deny thought to brutes, since whatever the beasts do can be accounted for mechanically, and to observe that were thought granted them, it would follow that they too had minds distinct from their bodies.

Cartesian dualism becomes the point of departure for several later theories which agree with none of its conclusions. Berkeley holds with Descartes that the soul always thinks, while denying that bodies exist at all; Spinoza retains the definition of mind as a thinking thing but denies that finite minds and bodies are substances; Locke accepts the union of two substances and rejects perpetual thought. The relation of thinking to extended substance is examined further under the ideas of Matter and Soul, and the question of mind in brutes under the idea of Animal.

The opening chapters of the Leviathan set out an account of mind in which nothing immaterial is admitted. There is no conception in a man's mind which has not first been begotten upon the organs of sense, and sense itself is motion, the pressure of external bodies communicated by the nerves to the brain and heart. Imagination is defined as decaying sense, and memory as imagination considered under the aspect of its decay; dreams are the imaginations of the sleeping, arising from the agitation of the inward parts. Thought on this showing is not the reception of intelligible forms but the motion of matter, and Hobbes belongs in this respect with Lucretius, though the two differ in much else.

Reasoning is described as reckoning. When a man reasons, Hobbes writes, he does nothing but conceive a sum total from the addition of parcels, or a remainder from the subtraction of one sum from another, and what is added or subtracted are names. Words are the counters of this arithmetic, serviceable as marks and signs but empty in themselves; truth and falsity are properties of propositions rightly or wrongly joined, not of things apprehended. Error accordingly arises from miscounting, from the ambiguity of words, from taking metaphors for definitions, and from the use of terms to which no conception answers, of which "incorporeal substance" is his standing example.

Since there is no separate intellect and no abstraction of universals, the differences between men and beasts must be accounted for otherwise. Hobbes assigns them chiefly to speech, by which trains of imagination are registered, general names imposed, and consequences reckoned that the beasts, lacking names, cannot reckon. The passions receive a parallel treatment as small beginnings of motion within the body, and deliberation is described as the alternate succession of appetites and aversions ending in the act of willing. These consequences for conduct and for the authority of the sovereign are considered further under the ideas of Will, Liberty, and Language.

The reduction of mind to matter, and of reasoning to computation with names, raises a difficulty about the standing of what is reckoned. If general names are imposed by agreement, then the truths of geometry and of moral philosophy would seem to depend upon that agreement rather than upon the natures of things. Locke, who accepts that all ideas arise from experience, nonetheless seeks to preserve a knowledge that is certain; Hume presses the question further and concludes that much of what passes for knowledge is custom. The materialist position is examined at length under the idea of Matter, and its bearing on liberty under the idea of Necessity.

Locke conceives the mind as a soul or spirit possessing many distinct powers, among them the powers of sense and imagination as well as those of abstraction and reasoning, and the voluntary powers of choosing and willing. The first book of the Essay is given over to the denial of innate ideas and principles, and the second to the account which is to replace them. The mind at the outset is white paper, void of all characters and without any ideas, and it comes to be furnished from experience alone, whether by sensation, which conveys ideas of external sensible objects, or by reflection, which is the mind's perception of its own operations.

From simple ideas so received the understanding builds the rest. It combines them into complex ideas, sets them side by side in relations, and separates them from the circumstances of their occurrence by abstraction; and the ideas of substance, of power, of infinity, and of God are traced back in this manner to the materials furnished by the two fountains of experience. Locke agrees with Aristotle in denying anything to the intellect that was not first in sense, but he does not accept the Aristotelian separation of sense from intellect as distinct faculties with distinct objects, nor does he think an agent intellect required to account for the mind's general ideas, a point on which Berkeley and Hume oppose him in turn.

Against Descartes he denies that the soul always thinks. Experience assures us that we sometimes think, and thence that there is something in us with the power to think; whether that substance thinks perpetually, experience does not inform us, and dreamless sleep may well be an affection of the whole man, mind as well as body. Locke further distinguishes primary qualities, such as extension, figure, and motion, which belong to bodies themselves, from secondary qualities, which are powers in bodies to produce ideas of color, sound, and taste in us. The reliability of the understanding rests for him on tracing its ideas back to their origins, and its limits are set by the same means.

Locke's position is agreed with and departed from in different directions at once. Berkeley holds with Descartes that the soul cannot cease to think without ceasing to be, and disputes the doctrine of abstract general ideas; Hume, retaining the derivation of all ideas from impressions, argues that what is thereby certain concerns only relations of ideas and tells us nothing of matters of fact; Kant argues that the account of experience is itself defective, the mind contributing more to experience than a blank receptivity could contribute. The origin of ideas is treated more fully under the idea of Idea, and the extent of what the understanding can attain under the idea of Knowledge.

Hume takes over from Locke the derivation of all ideas from what experience supplies, and carries it to a conclusion Locke did not draw. Entering most intimately into what he calls himself, he says, he stumbles always on some particular perception of heat or cold, light or shade, love or hatred, and never on any impression of a simple and continued self apart from these. The mind is on this account nothing but a bundle or collection of different perceptions succeeding one another with inconceivable rapidity. What Descartes and Locke alike had taken for a substance in which thinking resides is thus set aside, though Hume nowhere denies that thinking occurs.

Personal identity is accordingly explained as something the imagination supplies rather than something observation discovers. Finding resemblance among successive perceptions, and passing easily along the chain of them, the imagination confounds the succession with an identity and feigns a continuing subject to bear it. Substance, causal connection, and the continued existence of bodies are referred to the same principles of association, which Hume proposes as a kind of attraction in the mental world answering to gravitation in the natural one. The consequences of this treatment of cause are pursued under the ideas of Cause and Necessity.

The denial of substance does not, however, carry with it a denial that the mind has distinct powers. Whatever the mind may be, and however it exists, Hume holds it cannot be doubted that it is endowed with several powers and faculties, that these are distinct from one another, and that the obvious distinctions between will and understanding, or imagination and passion, fall within the comprehension of every human creature. If we can go no further than this mental geography, the delineation of the parts and powers of the mind, it is at least, he thinks, a satisfaction to have gone so far. He acknowledges elsewhere that the reasonings which lead to the bundle leave him in a melancholy he cannot dispel by argument, and that nature relieves it where philosophy cannot.

Hume leaves the unity of the mind to be accounted for by others. Kant takes the problem up by locating that unity in a formal condition of experience rather than in a substance or a fiction, and describes his own awakening from dogmatic slumber as owing to Hume. William James, who ranks Hume with Locke on the analysis of mind into powers and contents, returns to the flow of perceptions and redescribes it as a stream in which relations are felt as directly as the terms they join. The question of what makes a man the same man over time is treated more fully under the ideas of Same and Other and of Memory and Imagination.

In Kant's account mind is neither a faculty of the soul, nor a thinking substance, nor a spirit endowed with a diversity of powers. All our knowledge, he writes, begins with sense, proceeds thence to understanding, and ends with reason, beyond which nothing higher can be discovered in the human mind for elaborating the matter of intuition and subjecting it to the highest unity of thought. The three faculties have distinct offices: sense is the faculty of intuition, understanding the faculty of judgment and of scientific knowledge, and reason a faculty which regulates and criticizes within the sphere of thought. Mind names the unity and order of this triad rather than a being in which the triad inheres.

Experience is on this view never a mere succession of impressions. Whatever is given in intuition is given under the forms of space and time, and whatever is thought about it is thought under the categories of the understanding, among them substance, cause, and community. Since these forms and categories are contributed by the knowing mind and not derived from what is known, the inquiry proceeds by asking how objects must conform to the conditions of knowledge rather than how knowledge conforms to objects. This reversal, which Kant compares to the hypothesis of Copernicus, is what permits him to hold that certain propositions are both necessary and informative about the world of appearances.

The unity of experience is traced in turn to what Kant calls the transcendental unity of apperception, the "I think" that must be able to accompany all representations if they are to be mine. It is not the substantial soul of Descartes, nor a fiction of the imagination as with Hume, but a formal condition of any connected experience whatever. From this it follows that the mind as it is in itself is not among the things we know, and the Transcendental Dialectic is given over to showing how reason falls into paralogism when it argues from the unity of the "I think" to the simplicity, substantiality, and immortality of the soul. The limits so drawn are examined further under the ideas of Knowledge and Metaphysics.

After Kant the subject is described less as a thing whose nature is to be discovered than as a set of conditions under which experience is possible. Hegel takes the conditions to be phases in the unfolding of an absolute mind, so that what Kant confined to the structure of knowledge becomes the structure of reality and of history alike, a view whose expression appears in the chapters on History and State as well as here. Others, William James among them, question whether the transcendental ego is required at all, once the continuity of the stream of thought is described as it is actually found.

James proposes to describe mind as the psychologist finds it rather than as metaphysics requires it to be. He is willing to posit a soul influenced in some manner by brain states and responding to them by conscious affections of its own, but he observes that the immediately known thing which stands in apposition with the brain process is the state of consciousness and not the soul. What the soul is, and whether it exists, he leaves to metaphysics. So far as observation and analysis are concerned, the phenomena of mind are to be found in the stream of thought, and the words "feeling" and "thought" are used to cover every mental operation whatever, sensations and emotions and wishes no less than conception and reasoning.

Where Locke and Hume divide the mind by types of operation into powers, James divides it rather by types of content into states, and lays stress on the connection of those states in a continuous flow. Consciousness, he says, does not appear to itself chopped into bits; the transitions and fringes and feelings of relation are as real as the substantive parts they join, and associationism errs in resolving the stream into discrete atoms. Every thought tends to be part of a personal consciousness, is always changing, is sensibly continuous with what precedes it, deals with objects independent of itself, and welcomes some of those objects while rejecting others, attention being on this account a form of selection.

In the chapter on the self James distinguishes the "I," the knower or passing pulse of thought, from the "Me," the known self, which comprehends the body, its possessions, its social standing, and its inner life. The passing thought, he suggests, is the only thinker psychology requires, since each present thought appropriates what came before. He proposes further that the pursuance of future ends and the choice of means for attaining them are the mark and criterion of the presence of mentality, a criterion which bears directly on the comparison of men with animals treated under the ideas of Animal and Man. On the relation of mind to body he declines both the doctrine of their complete independence and the mind-dust theory that would scatter a particle of consciousness through every particle of matter.

The description of the stream of thought supplies later inquiry with a body of phenomena that any theory of mind must accommodate. Freud follows James in attending to the dynamic interaction of mental contents and carries the account of purposive tendency further, tracing it to instinctual sources of which the thinker is unaware. The physiological conditions of mental activity, which James examines at length in the earlier chapters of the Principles, are discussed further under the ideas of Matter and Medicine.

Freud denies the identification of mind with consciousness which the modern tradition after Descartes had generally assumed. Consciousness is for him a quality of mental acts and not their defining character, and the greater part of mental life proceeds without it. He distinguishes two kinds of unconscious, that which is latent and capable of becoming conscious, and that which is repressed and not capable of becoming conscious in the ordinary way; the first he calls preconscious, reserving the term unconscious for the second, so that three terms are required where the tradition had used one. The evidence adduced for the distinction is drawn from dreams, from errors of speech and memory, and from the symptoms of neurosis.

To this description of mental contents is joined an account of psychic structure. The id is the reservoir of instinctual demand, governed by the pleasure principle and knowing neither contradiction nor time. The ego develops out of the id under the influence of the external world, and undertakes to represent reason and the reality principle against the passions of the id, though its power over them is limited and much of it is itself unconscious. The super-ego, formed by the internalization of parental and social authority, exercises the offices of conscience and self-observation and is the source of guilt. Mental life is described as a transaction among these three agencies and the demands of the outer world.

Freud identifies psychic energy in general with what he calls libido, and holds that mind in its most primitive form has wholly the aspect of desire or seeking, expressing itself in two fundamentally different classes of instincts, the sexual in the widest sense of the term and the aggressive, whose aim is destruction. He counts the resulting picture the third of the blows dealt to human self-love, after the astronomical and the biological, in that man is shown not to be master in his own house. The pathological states from which the account was derived, and the therapy that accompanies it, belong more properly to the chapters on Medicine and Desire.

Whatever is made of the particular agencies Freud distinguishes, the topography of mind he proposes has kept its place in subsequent discussion, and the question whether the mind is transparent to itself is no longer answered as it was by Descartes and Locke. The doctrine bears also on the older question of the relation of reason to desire, treated under the ideas of Desire and Will, and on the account of madness and its causes, treated under the idea of Medicine.