What is Plato's Theory of Forms?
The Theory of Forms posits that the objects we encounter in the sensible world are imperfect copies of perfect, eternal, and immutable Forms. These Forms are not physical but exist in an intelligible realm accessible only through reason. For instance, all particular beautiful things participate in the Form of Beauty, and all just actions participate in the Form of Justice. True knowledge, therefore, is not of the changing physical world but of these unchanging Forms, attained through intellectual ascent.