Idealism

Idealism is any philosophical theory which considers that the ultimate nature of reality rests on the mind, on abstract forms, or on mental representations.

From the point of view of the philosophy of knowledge, idealism (reality is abstract and concrete, mental, etc.) is opposed to realism, which asserts that the external world has an existence independent of consciousness and knowledge that we can have.
From the point of view of the philosophy of mind, idealism (reality is spirit) is opposed to materialism, which asserts that ultimate reality is matter.

In everyday language, idealism is the attitude of someone who directs his thoughts and actions according to an ideal.

A multiple concept

This very general pattern is broken down into so many variants of idealism that there are ways of relativising reality for the benefit of any conceptualized world or conceptualization itself:

Idealism can first consist in removing all appearance from reality, phenomena being in reality representations of the mind;
Idealism can consist in asserting that thought is the only certain reality; any other being in the realm of conjecture;
The world itself assimilated analogically to a thinking being (point 2), idealism still consists in supposing the derivation of beings and reality from a spiritual principle (thought, consciousness, concept, etc.). This definition is at the basis of the separation of the global domain of philosophy into two fundamental branches: idealistic philosophies (Plato, Anaxagoras especially, Hegel, Teilhard de Chardin, etc.) which posit that “the mind is the substratum of the matter,” and materialistic philosophies (Diogenes, Democritus, Marx, Bertrand Russell, etc.) which, on the other hand, posit that “matter is the substratum of the mind.” In formal logic, these two approaches to “ultimate reality” are not reconcilable: one can not be both idealistic and materialistic.
In the next degree, idealism affirms the true existence of a conceptual world (realism of the intelligible); with many variations according to the pregnance or influence of this universe on the sensible world if it remains;
Finally, any possible form of sensible reality having become insignificant, another idealism is summed up in reducing the essence of being to thought or consciousness.

Not applying to the same object and for good reason, the postulates of these idealisms can be more or less contradictory. It seems difficult, for example, to think of thought as the only reliable reality and to advance at the same time the hypothesis of a more transcendental reality.

Idealism in Antiquity

For Plato, reality is not divided into “two kinds” of things, the visible and the invisible, but there is only one reality of intelligible type (improperly called “intelligible world”) in which the visible world participates and holds his reality.

In the visible world we must distinguish what is of the order of:

living beings, plants and objects of human manufacture;
image ;
1. the shadows (it is from a shadow that the first image was made, as established by the myth of Dibutade (Pliny the Elder, Natural History, Book 25, Chapter 152);
2. ghosts: reflections (e.g. Narcissus) or polished surfaces (example: the shield of Perseus) and other representations due to the hand of man.

The images are imitations of the first category (models), but the images only imitate the appearance of the model. They cannot bring us closer to the knowledge of the object.

In the intelligible world we will distinguish:

“discursive knowledge”, that which is based on hypotheses or on the observation of models. Here we would classify all sciences, both human and experimental.
“dialectical intelligence”, the one that is interested in the principles that govern all things without going through the example or “modeling”.

In the last limits of the intelligible, only the philosopher can perceive the idea of good. In other words, ideas are of a higher order and it is up to man to rise to them. Thus Plato makes from the philosophy the tool of true knowledge.

Plato’s idealism sometimes opposes the realism of Aristotle. But Ideas have an existence independent of us: Plato is therefore a realist, but a realist of the intelligible. Aristotelianism is then considered as a variant of Platonism, which is essentially distinguished by the immanence of these principles.

Another opposition to Plato’s idealism lies in the atomism of Leucippus and Democritus, whose theories are purely materialistic. For them, the universe consists only of voids and atoms.

Modern idealism

When ancient idealism was content to enhance the intelligibility of the world in one way or another, modern-day thinkers have sometimes pushed the logic of this relativisation of sensible reality. Over the course of time, from idealization to reinforcement of subjectivity, the credit in the exteriority of the world has been reduced to a trickle and modern idealism is weakly resisting the temptation to deny the “otherness” of the reality, which is reduced in its totality to the intelligible.

Descartes, “problematic” idealism (“empirical” idealism, according to Kant): thought is the most obvious reality, the reality of the outside world is problematic. Only God can guarantee it.
Leibniz, “monadic” idealism: the substances are spiritual, and God establishes a harmony between them.
Berkeley, subjective idealism or “immaterialism” according to the name of its author: matter is an ontological fiction. Berkeley considers that consciousness mistakenly attributes objectivity to what is merely an ideal production. This doctrine denies, therefore, that one can know the external world as it is since it does not exist in itself but only in thought. A famous formula summarizes it: Esse is percipi aut percipere (“To be is to be perceived or to perceive”) (Principles of human knowledge, 1710).
Kant and Husserl, “transcendental” idealism: Kant’s legacy appears as the need to find and construct a system in which man, God and the world can be understood in a synthetic unity, as a discourse on all beings in which man stands as their highest articulation according to Hans Huin. Here again, there is no idealism in the strict sense, Kant’s position being more nuanced (Kant also opposing pure idealism): the only knowable reality is phenomenal, given in the transcendental framework of space and time (transcendental idealism), but only experience provides a valid material for knowledge (empirical realism).
- Schopenhauer, “transcendental” idealism similar to that of Kant with one great exception: the world is both my representation (the Kant phenomenon), and a non-rational principle devoid of knowledge, the Will (the thing in itself or the Kant’s noumene); but, in Schopenhauer, we come to know the thing in itself by the experience of the human will, which should not be confused with the Will but which is its highest degree of objectification.
Hegel, absolute idealism: the only reality is the absolute Spirit, the mind is everything and everything is spirit. Absolute Spirit is also universal Reason: “What is rational is effective, and what is effective is rational” (Philosophy of Law, preface).

Idealism in India

The Buddhist school mahayana yogacara-vijnanavadin (chittamatra) is “the only example of an idealist doctrine in India, although the Hindus understand something else under the term of Indian idealism, namely the affirmation [Hinduism] of atman (âtma-vâda), which is being-knowledge-bliss (sat-cit-ananda).”