In discussing this term and its meaning, reference must be had to the cognate expressions, idealist, idealized, ideal (adjective), and the ideal (noun), all of which are derived from the Greek idéa. This signifies "image", "figure, "form": it can be used in the sense of "likeness", or "copy" as well as in that of "type", "model", or "pattern": it is this latter sense that finds expression in "ideal", and "the ideal" and the derivatives are mentioned above. In speaking of "the ideal", what we have in mind is not a copy of any perceptible object, but a type. The artist is said to "idealize" his subject when he represents it as a fairer, nobler, more perfect than it is in reality.
Idealism in life is the characteristic of those who regard the ideas of truth and right, goodness and beauty, as standards and directive forces. This signification betrays the influence of Plato, who made idea a technical term in philosophy. According to him the visible world is simply a copy of a supersensible, intelligible, ideal world, and consequently "things" are but the impress stamped on reality by that which is of a higher, spiritual nature.
Platonism is the oldest form of idealism, and Plato himself the progenitor of idealists. It is usual to place in contrast Plato's idealism and Aristotle's realism; the latter in fact denies that ideas are originals and that things are mere copies; he holds that the essence is intelligible, but that it is immanent in the things of nature, whereas it is put into the products of art. It is more correct, therefore, to call his teaching an immanent idealism as contrasted with the transcendental idealism of Plato. Both these thinkers reveal the decisive influence of that moral and æsthetic idealism which permeated Greek life, thought, and action; but for both, what lies deepest down in their philosophy is the conviction that the first and highest principle of all things is the one perfect spiritual Being which they call God, and to which they lead back, by means of intermediate principles--essence and form, purpose and law--the multifarious individual beings of the visible world. In this sense idealism is dualism, i.e. the doctrine of a higher spiritual principle over against that which is lower and material; and this doctrine again is clearly opposed to the monism which would derive the higher and the lower alike out of one and the same All-being. This older idealism teaches, not that there is One-All, but that there is an alpha and omega, i.e. a supermundane Cause and End, of the world. By means of its principles, idealism maintains the distinctness of God and the world, of the absolute and finite, yet holds them together in unity; it adjusts the relations between reality and knowledge, by ascribing to things dimension, form, purpose, value, law, at the same time securing forethought the requisite certainty and validity; it establishes objective truth in the things that are known and subjective truth in the mind that knows them. In this sense the Schoolmen teach that forma dat esse et distingui, i.e. the principle which formally constitutes the object, likewise, in the act of cognition, informs the mind. Inasmuch as its principles express the cause and purpose of things, their determinate nature and value, idealism unites the speculative and the ethical, the true and the good, moral philosophy and the philosophy of nature.
In this sense St. Augustine developed the Platonic teaching, and in his philosophy is idealism in the genuine meaning of the term. From him comes the definition of ideas which Christian philosophy has since retained: "Ideas are certain original forms of things, their archetypes, permanent and incommunicable, which are contained in the Divine intelligence. And though they neither begin to be nor cease, yet upon them are patterned the manifold things of the world that come into being and pass away. Upon these ideas only the rational soul can fix its gaze, endowed as it is with the faculty which is its peculiar excellence, i.e. mind and reason [mente ac ratione], a power, as it were, of intellectual vision; and for such intuition that soul only is qualified which is pure and holy, i.e., whose eye is normal, clear, and well adjusted to the things which it would fain behold" (De diversis quaest., Q. xlvi, in P.L., XL, 30).
This line of thought the Scholastics adopted, developing it in their treatises as ideology. Their theory is described not as idealism, but as realism; but this does not imply that they are in conflict with the doctrine of Augustine; it means rather that the ideal principles possess real validity, that as ideas they subsist in the Divine mind before the things corresponding to them are called into existence, while, as forms and essences, they really exist in nature and are not really products of our thinking. In this last-named sense, i.e., as subjective constructions, ideas had long before been regarded by the philosophers of antiquity and especially by the Stoics, who held that ideas are nothing else than mental representation. This erroneous and misleading view appeared during the Middle Ages in the guise of nominalism, a designation given to the system whose adherents claimed that our concepts are mere names (nomina), which have as their counterparts in the world of reality individual things, but not forms or essences or purposes. This opinion, which robs both science and moral principles of their universal validity, and which paves the way for Materialism and agnosticism, was combated by the leaders of Scholasticism--Anselm of Canterbury, Albertus Mangus, Thomas Aquinas, Bonaventure, and Duns Scotus--nevertheless, from the fourteenth century onwards, it had its champions and propagators, notably William of Occam. For the untrained mind it was easier to consider individual things as the only realities and to regard forms and essences as purely mental products.
So it came to pass that the word idea in various languages took on more and more the meaning of "representation", "mental image", and the like. Hence too, there was gradually introduced the terminology which we find in the writings of Berkeley, and according to which idealism is the doctrine that ascribes reality to our ideas, i.e. our representations, but denies the reality of the physical world. This sort of idealism is just the reverse of that which was held by the philosophers of antiquity and their Christian successors; it does away with the reality of ideal principles by confining them exclusively to the thinking subject; it is a spurious idealism which deserves rather the name "phenomenalism" (phenomenon, "appearance", as opposed to noumenon, "the object of thought").
The doctrine of Descartes has also per nefas been called idealism. It is true that Cartesianism is in line with the genuine idealism of the earlier schools, inasmuch as it postulates God, thought, and spatial reality. But, on the other hand, this system too employs idea only in a subjective signification and quite overlooks the intermediate position of ideal principles. According to the theory of Leibniz, which has also been regarded as idealistic, our mind constructs from its own resources (de son propre fond) its scheme of the world; but, thanks to a pre-established harmony (harmonie préétablie), it accords with reality. This view, however, furnishes no solution for the epistemological problem. Kant claims that his critical philosophy is both a "transcendental idealism" and an "empirical realism"; but he declares ideas are "illusions of reason", and such ideal principles as cause and purpose are simply devices of thought which can be employed only in reference to phenomena. Fichte took Kant as his starting--point but finally rose above the level of subjectivism and posited a principle of reality, the absolute Ego. Hegel's doctrine can be termed idealism so far as it seeks the highest principle in the absolute idea, which finds its self-realization in form, concept, etc.--a view which amounts virtually to monism. The various offshoots of Kantian philosophy are incorrectly regarded as developments of idealism; it is more accurate to describe them as "illusionism" or "Solipsism", since they entirely sweep away objective reality. In this connection a German philosopher declares:
I affirm without hesitation that the assertion, 'the existence of the world consists merely in our thinking', is for me the result of a hypertrophy of the passion for knowledge. To this conclusion I have been lead chiefly by the torture I endure in getting over 'idealism'. Whosoever attempts to take this theory in downright earnest, to force his way clean through it and identify himself with it, will certainly feel that something is about to snap in his brain (Jerusalem, "Die Urtheilsfunktion", Vienna, 1886, p. 261).
Similar conclusions are reached by J. Volkelt (Erfahrung u. Denken, Hamburg, 1886, p. 519);
Any man who carries his theoretical doubts or denial of the external world so far that even in his everyday experience he is forever reminding himself of the purely subjective character of his perceptions. . .will simply find himself flung out of the natural course and direction of life, stripped of all normal feeling and interest, and sooner or later confronted with the danger of losing his mind completely.
It is certainly a matter of regret that the terms idea, idealist, and idealism, originally so rich in content, should be so far degraded as to signify such aberrations of thought. The present writer, in his "Geschichte des Idealismus" (2nd ed., Brunswick, 1907) has taken the ground that the original meaning of these terms should be restored to them. In the index of this "Geschichte" and in his monograph, "Die Wichtigsten Philosophischen Fachausdrücke" (Munich, 1909), he traces in detail the changes and meaning which these words have undergone.
APA citation. (1910). Idealism. In The Catholic Encyclopedia. New York: Robert Appleton Company. http://www.newadvent.org/cathen/07634a.htm
MLA citation. "Idealism." The Catholic Encyclopedia. Vol. 7. New York: Robert Appleton Company, 1910. <http://www.newadvent.org/cathen/07634a.htm>.
Transcription. This article was transcribed for New Advent by Peter S. Zehr and Patrick C. Swain.
Ecclesiastical approbation. Nihil Obstat. June 1, 1910. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York.