He believed that, as well as the material world we live in and of which we experience; there is another world, an eternal world of concepts, or Forms. This eternal world is more real than the world we experience through the senses (or Empirical knowledge – knowledge based on our senses), and it is the object of knowledge, pure knowledge, not opinion.
Before Plato came up with this theory, philosophers before him, namely Heraclitus, viewed the world of as a subject of constant change. In a constant state of flux, things come into the world, they change all the time they are there and then they go away again. He believed the objects we perceive, are not eternal ‘things’, they are processes. There is nothing in the world that is reliable and unchanging, and nothing that we can hold up as a certain, unchanging truth.
Plato was more optimistic with his conclusions; he assumed that permanent truth could be found on a different plane – in a non-material world of Forms. He made many comparisons between our world and the real world. He stated that the real world was a non-material world that was outside time and space. It was known only through reason – which ultimately results in pure, permanent knowledge. There is no change eternally, so the world, and everything in it, is perfect.
Plato believed that there exists an immaterial Universe of `forms', perfect aspects of everyday things such as a table, bird, and ideas/emotions, joy, action, etc. The objects and ideas in our material world are `shadows' of the forms.
This solves the problem of how objects in the material world are all distinct (no two tables are exactly the same) yet they all have `tableness' in common. There are different objects reflecting the `tableness' from the Universe of Forms.
Also, our world is full of particular examples of objects, e.g. tables, dogs. There are also particular examples of qualities, such as beauty, or justice. All these ‘particulars’ are in a process of change, and are therefore imperfect. For Plato, this meant they must be inferior copies of some permanent universal object or quality. The permanent or universal objects and qualities could be found in the Real World – where everything was perfect, or ideal, and can be named the realm of Forms. Our world shows only shadows and poor copies of these Forms, and so is less real than the world of the Forms themselves, because the Forms are eternal and never-changing, the proper objects of knowledge.
As this theory could have baffled many, Plato put this concept into an Allegory, a fable if you like, named the Allegory of the Cave.
The allegory of the cave describes individuals chained deep within a cave. Bound so that vision is restricted, they cannot see one another. The only thing visible is the wall of the cave upon which appear shadows cast by models or statues of animals and objects that are passed before a brightly burning fire. The prisoners take these shadows to be the real objects – what we accept as true. One of the individuals is let free from the cave into the light of day. He finds it a struggle to adjust to the changes he is encountering – movement, the differences in the objects he sees, and the light. With the aid of the sun, that prisoner sees for the first time the real world and returns to the cave with the message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free of their bonds. However, the prisoners inside the cave mock and laugh at him, and threaten to kill him, and anyone who attempts to free them.
The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolizes the transition to the real world, the world of full and perfect being, the world of Forms, which is the proper object of knowledge. The prisoners represent most people, who do not question, and are content within their “comfort zone”. However, the prisoner who is let free, is a philosopher, namely Socrates, who is inquisitive and prepared to venture into the unknown. His first movements are painful because this shows how is hard to discover ‘new truths’, and that it is easier to stick with what we already know – in other words, to be ignorant. The prisoners’ gradual adjustment to the light shows we only learn through questioning, and the light, or the Sun, resembles ‘Goodness’ – warmth and light, essential to life.
Plato was telling us that we can only get to know the real world through a long and painful process, but if we are determined to do it, it is worthwhile, because we will gain ‘real knowledge’.
The theory of Forms may also be understood in terms of mathematical terms. A circle, for instance, is defined as a plane figure composed of a series of points, all of which are equi-distant from a given point. No one has ever actually seen such a figure, however. What people have actually seen are drawn figures that are more or less close approximations of the ideal circle. In fact, when mathematicians define a circle, the points referred to are not spatial points at all; they are logical points. They do not occupy space.
Nevertheless, although the Form of a circle has never been seen, indeed, could never be seen, mathematicians and others do in fact know what a circle is - that they can define a circle is evidence that they know what it is. For Plato, therefore, the Form "circularity" exists, but not in the physical world of space and time. It exists as a changeless object in the world of Forms or Ideas, which can be known only by reason. Forms have greater reality than objects in the physical world both because of their perfection and stability and because they are models. Circularity, squareness, and triangularity are excellent examples, then, of what Plato meant by Forms. An object existing in the physical world may be called a circle or a square or a triangle only to the extent that it resembles ("participates in" is Plato's phrase) the Form "circularity" or "squareness" or "triangularity” in the real world.
However, there then comes the question, how do we know what is perfect, or what a circle is and what it should look like? Plato answered this as well. He understood that knowledge is recollection or remembering. We have an innate, or inborn understanding of the Forms, e.g. Beauty, Justice. Because we have concepts or ideas of the Ideal Forms, even though we haven’t experienced them, our souls must have known what the Forms were. This leads on to his belief that people have an immortal soul, which has been passed through a series of embodied and disembodied state. We have to awaken this knowledge from previous existences. He called this Anamnesis. In other words, Plato believed in re-incarnation of the soul, and because it has been around before, our soul tells us what is beautiful, or just, etc.
Plato also said that philosophers obtain all this knowledge of what is perfect, etc because they work hard to do this. The philosopher has knowledge of this world and can use it to explain the existence of everything. The ignorant do not understand because they are satisfied with their world of appearances and are happy with the life they have. They are confident that what they see is real and do not want to know of an alternate world.
Plato conceived the Forms as arranged hierarchically; the supreme Form is the Form of the Good, which, like the sun in the allegory of the cave, illuminates all the other Ideas. Next, in the hierarchy of the Forms, are the universal qualities, such as justice and truth, after them, come the concepts and ideas. The fourth stage in the hierarchy, or order of importance are physical living objects, e.g. humans, and after them, the physical inanimate objects, for example a book or a chair.
Ultimately, the theory of Forms is intended to explain how one comes to know and also how things have come to be as they are. In philosophical language, Plato's theory of Forms is both theory of knowledge and theory of being. The people who have the most knowledge of this will be philosophers, so they should rule. We can get to gain ‘real knowledge’ – this knowledge is certain, there is a right and there is a wrong, whereas the knowledge we are normally used to –‘ Empirical knowledge’ is largely based on opinion and is therefore not accurate. It is a long, painful process to real knowledge, but extremely worth it.