On the death of Plato in 347, Aristotle moved to Asia Minor, where he spent some years devoted principally to the study of biology and zoology. In 343 he moved to Pella, where he served as tutor to King Philip's son, the future Alexander the Great. (What influence Aristotle may have had on that obnoxious young man is uncertain.) After further migrations, Aristotle returned to Athens in 335, and for the next decade engaged in teaching and research in his own school in the Lyceum. He fled from Athens on the death of Alexander in 323, and died a year later in Chalcis. His will, which has survived for us to read, is a humane and touching document.
Aristotle was a polymath: his researches ranged from abstract logic and metaphysics to highly detailed studies in biology and anatomy; with the possible exception of the mathematical sciences, no branch of knowledge was left untouched by him. His contributions were both innovatory and systematic: no one man has achieved more, no one man has had greater influence, and Aristotle remains, in Dante's phrase, 'the master of those who know'.
Aristotle's main contributions to the study of mind are to be found in his treatise De anima (On the Soul or Concerning Psyche) and in a series of short papers known collectively as the Parva naturalia. He regarded the study of psychology as a part of the general study of animate nature (see psyche): there is no division in his thought between the study of mind and the study of matter, and his psychological writings are continuous with his overtly biological works.
An early work, the Eudemus (only fragments of which survive), betrays a juvenile interest in a Platonic account of the psyche: there Aristotle argued that the psyche was independent of the body, pre-existing it and surviving its death. But that separation of mind from body is foreign to Aristotle's mature works: in the De anima he defines the psyche as 'the first actuality of a natural organic body'; and he associates psyche with the animate functions of nutrition, perception, thought, and motion. Psychology is thus by definition linked to the biological sciences, and Aristotle explicitly states that the student of the psyche must investigate the behavioural and physiological aspects of his subject — he must know, for example, that anger is the boiling of the blood around the heart.
Perception receives a lengthy discussion in the De anima and in the De sensu, a component treatise of the Parva naturalia. Aristotle regards perceiving as a special sort of change in the perceiver: objects of perception, acting via some medium of perception, causally affect the perceiver's sensory apparatus; the apparatus changes inasmuch as it 'receives the form of the object without its matter', and that change is perception. For example, if you look at a white piece of paper, your eyes (or some part of them) actually become white: the eyes are made white by the paper, although no material part of the paper enters them. Similar stories are told of the other four senses. (Aristotle thinks he can prove that there can be no more than five senses.) Each sense has its own 'proper objects' (colours for sight, sounds for hearing, etc.), but some objects (for example, shape, size, motion) are 'common' to two or more senses. Other objects (men or trees, say) are perceived only 'accidentally' or indirectly: you see a man by virtue of seeing something white and moving, which happens to be a man.
The different sense modalities are somehow unified by a 'common faculty', sometimes called the 'common sense'; that faculty, which is located in the heart, is employed to explain various perceptual and quasi-perceptual phenomena, the most important of which is the 'unity of consciousness'. Colours are perceived by way of the eyes, sounds by way of the ears; but nevertheless, both perceptions belong to one and the same unitary subject or perceiver, who can compare and associate the data given by the two senses. By my eyes I see the colour and shine of the trumpet; by my ears I hear its tones: but it is a unitary I who perceives the trumpet, and I perceive the trumpet as a unitary substance. That task of perceptual unification is performed by the 'common sense'.
Perception is fundamentally a physical change, and it leaves physical traces in the body. Aristotle refers to those traces as 'phantasms', and they constitute the objects of phantasia or the faculty of imagination. The imagination is invoked in a number of contexts: thus it has an important role to play in the analysis of memory, which Aristotle discusses in his De memoria, and in the account of sleep and dreaming which he gives in the De somno and De somniis. (All three works are parts of the Parva naturalia.) Most importantly, the imagination supplies the link between perception and thought.
Aristotle's account of thought or 'the intellect' (nous) is one of the most perplexing aspects of his mental philosophy. On the one hand, he tends to treat thought on the model of perception: thought, like perception, is a change, and in thinking of things the mind somehow 'becomes' what it is thinking of (as the eye becomes what it is seeing, for example, white). Less obscurely, Aristotle holds that thought is dependent on imagination, and hence on perception: phantasms are, or represent, or accompany, the objects of thought, and we cannot think without phantasms. Since phantasms are the traces of perceptions, it follows that we cannot think without having perceived, and that the scope of our thought is determined by the extent of our perceptual experience. On the other hand, that strongly empiricist approach to the problems of thought seems to be modified by some remarks in one of the most celebrated and painfully difficult chapters in the whole of the Aristotelian corpus: in De anima, iii. 5, Aristotle distinguishes between two types of intellect: one, the 'passive' intellect, is securely tied, by way of phantasms, to perception and the body; the other, the 'active' intellect, is pure and unmixed, free from physical trappings, and capable of independent and eternal existence. The 'active' intellect has been discussed for more than 2,000 years, and scholars are no nearer understanding Aristotle's doctrine than was his own first pupil, Theophrastus. It is legitimate to suspect that Aristotle's brief notes on the two varieties of nous represent no more than a passing fancy or a temporary aberration; in any event, their presence in the De anima should not blind us to the fact that for the most part that treatise is uncompromisingly empiricist and materialist in its doctrines.
Movement is treated in the De anima, and also in certain of Aristotle's ethical and biological works. (The short treatise On the Movement of Animals is a particularly rich source for Aristotle's views on the subject.) Aristotle's treatment is remarkable for its attempt to combine a physiological explanation of animal locomotion (in terms of 'spirit' or pneuma, which runs through the body like current in an electric motor) with a psychological account in terms of desire and thought (imagination and perception). The physiology is inevitably crude, but Aristotle's aim is sophisticated: he thinks it possible to account for animal (and human) movements purely in terms of the physical events taking place in the body, while at the same time he wants to explain action, at a philosophical or analytical level, by way of the interaction of desires and beliefs. The attempt to combine those two approaches raises questions of their mutual consistency: Aristotle did not face up to those questions, but it is fair to observe that the issue is still a central and unresolved problem in the philosophy of the mind.
An outline survey of Aristotle's psychological theories does scant justice to his contributions to the subject; indeed, it may have the unwanted effect of belittling those contributions, since it is bound to stress the more abstract or general elements in Aristotle's thought. It is above all in the detail — both scientific and philosophical — of his account that Aristotle's genius shines out: a single page of his own writings will reveal more clearly than any summary the perspicuity, the intellectual acumen, and the scientific richness which justify his pre-eminence in the history of the study of mind and its place in nature.
(Published 1987)
— Jonathan Barnes
The standard translation of Aristotle, and the only complete English translation, was prepared by several scholars under the general editorship of J. A. Smith and Sir David Ross; usually known as the 'Oxford translation', it is now available in two volumes (revised by Jonathan Barnes) under the title The Complete Works of Aristotle (1984).
