Plato's theory of Ideas

According to Plato, the material world of the senses is an illusion. The real world, on the other hand, is the realm of Ideas which lies beyond the material world. With this view in mind, Plato claims that "only Ideas are real". The material world, or the world of appearances, is constantly changing. The world of Ideas, however, never changes and is free from the limitations of time and space. As a result, Plato's theory holds that Ideas represent true reality, or the Truth which transcends the relativity of matter.
Whereas the objects of the material world are apprehended by the senses, the Platonic Ideas are apprehended by the mind. The Greek words for Idea and Form are both related to the concept of vision. Thus, Ideas or Forms are things which are seen. However, they are not seen with the physical sight of the senses but rather "by a kind of intellectual vision". The mind which is capable of visualizing the higher realm of Ideas is often equated with the soul.
Beyond words to the Ideas which are embodied in them. Again, words are seen as being representations of the Ideas which are the true source of knowledge. Thus, "behind the words rise the genuine, ideal realities enshrined in the Theory of Forms, which alone are admissible as true objects of knowledge". In Cratylus, Socrates indicates that knowledge cannot be gained from the transitory things which constitute the material world. According to this argument, we cannot say that knowledge exists "if everything is in a state of transition and there is nothing abiding". Pure knowledge belongs to the realm of Ideas, which is beyond change and relativity. Socrates clarifies this by claiming: "But if that which knows and that which is known exist ever, and the beautiful and the good and every other thing also exist, then I do not think that they can resemble a process of flux". Therefore, Plato's theory holds that pure knowledge is to be found in the realm of Ideas rather than in the material world. The Symposium addresses these issues and shows that pure knowledge provides the ability to apprehend the Ideas of Truth and Beauty. The Symposium presents a series of speeches on the God of Love