Theory of forms

The Theory of Forms or Theory of Ideas, also known as Platonic idealism or Platonic realism, is a philosophical theory credited to the Classical Greek philosopher Plato.

A major concept in metaphysics, the theory suggests that the physical world is not as real or true as Forms (or Ideas, typically capitalized): the timeless, absolute, non-physical, and unchangeable essences of all things, which objects and matter in the physical world merely participate in, imitate, or resemble. In other words, Forms are various abstract ideals that exist even outside of human minds and that constitute the basis of reality. Thus, Plato's Theory of Forms is a type of philosophical realism, asserting that certain ideas are literally real, and a type of idealism, asserting that reality is fundamentally composed of ideas, or abstract objects.

Plato describes these entities only through the characters (primarily Socrates) in his dialogues, who sometimes suggest that these Forms are the only objects of study that can provide knowledge (as opposed to mere belief or opinion), and at other times contest the very existence of the Forms. The theory remains a general point of controversy in philosophy; nonetheless, it is considered to be a classical solution to the problem of universals.