There are four philosophical meanings of the word 'individual'. (1) A single being, as distinct either from a collection of beings or from the logical object of the general concept; a unique being; a being at least numerically distinct from all other beings. (2) A being that cannot be divided into parts to which the name of this being will apply. Thus a general name applies to a class of objects which can be divided into classes, to any one of which the class-name can still be applied, as Frenchmen, Germans, or Russians are all equally Europeans. But the name of an individual being, as for instance Socrates, cannot be applied to any of the parts, such as the hand or foot, into which Socrates can be divided. (3) An independent, separable being, capable of existing alone. (4) In ethics: A person, an individual as opposed to a corporation or a collection of men, or to a social group or organization. of any kind.
The concept of the individual is at once one of the most familiar and the most difficult both in the world of common sense and in the world of philosophy. That the beings which are to be found in the world, whether inanimate objects or living beings, whether material or mental, are individuals, _i. e. are distinct, singular, and unique, is a matter of common belief and report. But what constitutes individuality, or what is the principle of individuation, has been a matter of controversy both within the realm of special science and from the point of view of logical and metaphysical definition.
In logic the individual is opposed to the various kinds of universal concepts and classes, as, for example, to genus or species, or property, or accident. In psychology it has been frequently asserted that individual objects are the immediate objects of our perceptive experience; so that it has been frequently maintained, as sufficiently defining the nature of an individual being, that an individual is any object perceived by the mind as an external or as a real object. From this point of view the idea of individuality as a character of beings is derived directly from experience, and is irreducible to simpler ideas. As against this view, it has been maintained that the direct object of our perceptual experience is always a series or complex of definable or indefinable qualities, characters, relations, and behaviours of objects. Thus we observe than an orange is coloured, is round, is of a given weight, is in given relations to other observed objects, as for instance lying on a plate. But to observe these characters, however great their number and complexity, is still to observe characters that might be shared by other oranges, and frequently by other objects, so that it seems as if the individuality of the object were precisely what we least directly perceive. In case of individual persons, it is plain that we mean by personal identity a character which could never be made the object of any simple perceptive act; and in general the concept of individual being, in the various special sciences, as well as in metaphysical inquiry, shows many characters that cannot be derived from mere perception in any case. It is somewhat easier to regard the idea of individuality as an ultimate and indefinable idea, without giving any ground whatever, in experience or in articulate thought, for our overwhelming assurance that the objects with which we deal are individuals. Nevertheless, this way of treating the problem would be merely an abandonment of the question as insoluble; and accordingly we find in the history of thought a considerable number of efforts to define what has been called the principle of individuation. Such efforts have also played a part in the definitions
( 141) of the individual that have been framed to meet the exigencies at various special times.
II. History of the Principle of Individuation.
The problem of the nature of individuality is first reached in European philosophy as the result of those efforts at the definition of the logical method which assume definite form in the Socratic, Platonic, and Aristotelian doctrines. The Platonic ideas were beings supposed expressly to correspond to our general conceptions. A discussion of the nature of these ideas, and of their relations to one another and to the world of facts, of sense, and of ordinary experience, made prominent the question: What is meant by an individual? The problem in question is very explicit in the mind of Aristotle, though it cannot be said that he gave any very explicit solution of the questions that he himself raised. According to Aristotle, all beings in the universe are individuals, and universals have being only as realized in individual entities. On the other hand, science, according to Aristotle, is necessarily concerned with the universal, that is, with the laws and the ideal general characters possessed by facts. And yet, according to Aristotle, science undertakes to know being. Thus arises the familiar paradox of the Aristotelian system, that just that character of facts which science best knows is not that character which constitutes the true being of anything, since this true being is individual, and what science knows is universal. As to the principle of individuation, Aristotle is not explicit, except in the case where he is speaking of obviously corporeal entities, when he upon occasion says. that their material aspect is that which constitutes the individuality of any one being; while what he calls the form or general nature is common to many individuals.
The problem of definition of the individual became prominent in the philosophy of the Christian Church in the Middle Ages, especially owing to the importance which ethical individuality had acquired in Christian doctrine, and in consequence of the relation of individuality to the doctrine of the Trinity. In the early ages of
(142) scholastic philosophy, the discussion regarding the nature of universals was especially prominent, while from the age of Thomas Aquinas onwards, scholastic philosophy made especially important the principle of individuation and the nature of individuality. Here it was a classic Thomistic doctrine that, in the realm of nature, matter is the individuating principle, so that the purely incorporeal entities, such as the angels, could be individuated only by their form, and so that consequently, as the well-known Thomist theory maintained, two angels of the same species do not exist. The ethical individuals in the human world, according to Thomas, are genuine individuals, but they are individuated primarily by the different bodies to which the souls belong, so that when absent from the body, the soul, between death and the judgment, would be individuated by reason of what Thomas calls its inclinatio to a particular corporeal embodiment, an inclinatio which at the resurrection would be met by the presence of the glorified body of the saved or the equally permanent material organization of the lost. To the Thomistic Theory, Duns Scotus opposed the doctrine that a special form, called by him the haecceitas, is responsible for the individuation of every being, corporeal or incorporeal. This haecceitas, different in each individual, is something that is said to be `fused with the common nature,' in such wise that the doctrine of Duns Scotus especially lays stress upon the fact that the difference between individual. beings is a real and ultimate, non-corporeal, but not necessarily indescribable, character of each being--a character which a higher type of intelligence than our own may be able to appreciate, although it is admitted by Duns Scotus that this character is indefinable for our own human intellect.
In the philosophy of Leibnitz an effort is made to solve the problem of the individual by the famous principle of the identity of indescernibles. According to this principle it is impossible that two individuals in the universe could be precisely alike. And the unlikeness between individuals is always of an essentially
(143) describable or intelligible character. Were two individuals in all respects precisely alike, so that whatever was predicated of one was true of the other, these two individuals would be ipso facto identical, and difference of individuality means difference of quality or character.
Post-Kantian thought, during the idealistic period, laid most stress upon the definition of the ego, or of the ethical and epistemological person, and dealt with the problem of individuality mainly in this case. New in this period of thought, therefore, especially after Kant's theory of the unity of self-consciousness, are the Fichtean and Schellingean attempts to define the relations between a finite individual and the absolute ego. New is also the Hegelian definition of the individual as 'the unity of the universal and the particular.' In other words, Hegel held that when a universal law or principle, of the type that he defined as the Begriff, gets a complete development and expression, in respect of all the particular or specific aspects which the nature of this Begriff involves, such total expression of a universal law is as such an individual being, so that the problem with regard to the individual becomes identical with the problem as to the way in which universal principles can find complete or wholly satisfying expression in nature or in mind, or in general in experience.
Since the close of the idealistic period the problem of the individual has received discussion especially from three points of view. In the first place, in modern psychology and epistemology, efforts have been made to deal afresh with the problems of the nature of individuality in its most general form. The most familiar of these efforts is one not wholly unknown to earlier thought, very plainly stated by Schopenhauer, and frequently developed in recent works--an effort to make time and space the essential principles of individuation, to define the primary individual object as that which is in a given place, and at a given time, and to make the other forms of individuality derivable
(144) from this primary form of the idea by means of various associations between time and place, localization, and the various other characters possessed by moral or other types of individuals. The second point of view from which the problem has been discussed has been that of the biological sciences, and of the related branches of inquiry. Into these discussions this is not the place to go. The third point of view with regard to the individual has been that suggested by the ethical problem of the rights of the individual as a person, and of his relations to the social order. The revolt against certain eighteenth-century doctrines concerning the rights and position of the individual man has led to a number of forms of socialism and of ethical universalism, which have made light of the historical importance and of the moral value of the individual man. A frequent reaction against these very tendencies has led to a reassertion of individualism, which has been associated with various more or less novel efforts to restate the definition of the ethical indiyidual.
III. Meaning of Individual in the Sciences.
If we survey the problem of the individual apart from its history, it is easy to see that the question has several distinct forms, which may indeed be ultimately connected, but which are usually presented to our attention in quite different regions of inquiry. Amongst the sciences mathematics is prominent in dealing with individual objects, and systems of individual objects, which as artificial creatures of definition, or as very simple abstractions from our experience of space, ought apparently to be topics of easy and final agreement. Yet regarding the nature of all these forms of mathematical individuality considerable differences of opinion has existed amongst mathematical experts. Examples of mathematical entities that appear more or less obviously as individuals are the unit in arithmetic, the point in geometry, the line, when regarded as an elementary concept in some forms of geometrical investigation, and several other cases of objects which
( 145) are regarded as the elements of given mathematical systems. The question of the individuality, or at any rate of the singularity of such objects as space and time, viewed in their wholeness, has interested the mathematicians as well as the philosophers. In theoretical natural science, such concepts as the modern concept of energy, when compared with the usual concepts of matter, may well introduce the question whether recent theory is not really as much concerned with the problem whether universals exist, or whether individuals alone are real, as was ever scholastic doctrine. For energy as usually described appears to be an entity whose individuation is altogether problematic, and whose known character seems to be entirely of universal type. In the biological sciences the problem as to the living individual introduces entirely different questions and interests; and the problems of ethical individuality belong to still another realm of decidedly special character. Finally, the problem of the ultimate place of the category of individuality in the world at large remains as an issue for general metaphysics. It is, nevertheless, a fair question for philosophical inquiry whether all these so various problems are not really much more closely connected than they seem, and whether a final definition which will hold for all forms of individuality may not yet be discovered.