Plato’s Theory of Ideas
The Theory of Ideas
The theory of ideas is the core of Platonic philosophy, the axis through which all his thought is articulated. It is not expressed as such in any of his works, but treated from different aspects in several of his later works such as The Republic, Phaedo, and Phaedrus. It is generally believed that the theory of ideas is itself a Platonic theory, although several scholars of Plato, such as Burnet and Taylor, have defended the thesis that Plato took it directly from Socrates. Studies by D. Ross, among others, have highlighted the inadequacies of such an award, supporting the generally accepted interpretation.
The Traditional Formulation
The traditional formulation of the theory of Ideas is traditionally interpreted as follows: Plato distinguishes two modes of reality, one intelligible, which he calls the intelligible world, and another that he called sensitive, the sensible world. Intelligible reality, which he calls the “Idea,” has the characteristics of being immaterial, eternal (indestructible and ingenerable), being, therefore, outside of change, and is the model or archetype of the other reality, the sensitive, consisting of what we ordinarily call ‘things’. The sensitive world has the characteristics of being material, corruptible (subject to change, that is, generation and destruction), and is no more than a copy of intelligible reality. The first form of reality, made up of ideas, represents true being, while the second form of reality, the material realities or “things,” being in a constant state of becoming, can never be said to truly be. Also, only the Idea is capable of true knowledge or “episteme,” while sensible reality, things, are only likely to be opinion or “doxa.” The way in which Plato refers to the ideas in several of his works, such as in the Phaedo (the contemplative soul, before it joins the body, contemplates ideas) or in the Timaeus (the Demiurge models matter in accordance with the model of Ideas), and the assertion in Aristotle’s Metaphysics in which Plato “separated” Ideas from things, are often part of the traditional presentation of the theory of Ideas, including the statement of separation (“khorismós”) between the sensible and intelligible as a characteristic of it.
Dualism Sensible / Intelligible
One of the first consequences drawn from the traditional presentation of the theory of Ideas, then, is the “separation” between intelligible reality, also called the intelligible world (“kosmos noetos”) and sensuous reality or the visible world (“kosmos horatos”), which leads Platonic philosophy to a dualism that is the source of many problems for maintaining the theory, and that Aristotle pointed out as one of the fundamental obstacles to its acceptance. The intelligible world: Ideas, to the extent that they are the universal definition of the term representing the “essence” of the objects of knowledge, i.e., that which is within the concept, but with the peculiarity that it cannot be confused with the concept itself, means that Platonic Ideas are not mental contents, but objects to which mental contents (designated by the concept and expressed through language) relate. These objects or “essences” exist regardless of whether they are intended; they are distinct from thought, and as such enjoy similar features to those of the being of Parmenides. Ideas are unique, eternal, and immutable, like the being of Parmenides; they are not objects of sensitive knowledge, only knowable by reason. Not being the objective of sensitivity, they cannot be material. Yet Plato insists that they are entities that have a real and independent existence of both the subject and object of thought, which are essential, giving them a transcendent character. In addition, ideas are the model or archetype of things, so sensible reality is the result of copying or imitation of Ideas. For pluralistic philosophers, the relationship between the self and the world as we perceive it was the product of mixing and separation of the original elements (the four elements of Empedocles, the seeds of Anaxagoras, and the atoms of Democritus); Plato also had to explain the relationship between that reality that is immutable and that which is subject to change, i.e., between ideas and things. This relationship is explained as an imitation or participation: things imitate ideas, or participate in the Ideas.
The Sensible
For its part, sensible reality is characterized by being subject to change, mobility, generation, and corruption. The so-called problem of change leads Plato to find a solution that bears significant parallels with that proposed by the pluralist philosophers: following Parmenides, he must recognize the need for the immutability of being, but the sensible world cannot be seen as reduced to a mere illusion. Although its degree of reality cannot be compared to that of the ideas, it is to have any consistency, and cannot be equated simply with nothing. It is doubtful that we can attribute to Plato the intention of degrading perceptible reality to the point of considering it a mere illusion. The theory of Ideas aims to solve, among others, the problem of unity in diversity, and to explain how an element common to all objects of the same class, its essence, can be real, it seems clear that the claim of the reality of ideas cannot be achieved through the denial of all reality to things.