The Theory of Forms and the Ascent to Knowledge

At the heart of Plato's mature philosophy lies the Theory of Forms, a two-world metaphysics distinguishing the realm of Becoming, the changing, imperfect physical world perceived through the senses, from the realm of Being, the eternal, unchanging, and perfectly intelligible Forms (or Ideas) such as Justice, Beauty, Equality, and the Good. Particular things in the sensible world, a beautiful painting or a just action, are called beautiful or just only because they "participate" in, or imperfectly imitate, the corresponding Form; the Forms themselves are non-spatial, non-temporal, and accessible only to reason, not to sight or touch, making them for Plato the only proper objects of true knowledge.