Plato’s Contribution to Psychology (427-347 B.C.) He was the first person in history to produce a great all- embracing system of philosophy. He not only developed the theory of knowledge, theory of conduct, and a theory of state, but also the theory of universe. According to Plato, the soul has three parts or components, which he calls reason, spirit, and appetite. He discovered that there are three different kinds of activity going on in a person. First, an awareness of the goal or a value and this is the act of reason. Secondly, there is a drive towards action, the spirit, which is neutral at first but responds to the direction of reason. Last, there is the desire for the things of the body, the appetites. The body itself is inanimate, and therefore, when it acts or moves, it must be moved by the principle of life, the soul. In the body the soul experiences sensation, desire, pleasure, and pain as well as fear and anger. There is love, too, that can satisfy some taste to love of the truth or beauty that is pure and eternal.
The rational or thinking part is the highest in order When a person moves from believing to thinking, he moves from the visible world to the intelligible world, from the realm of opinion to the realm of knowledge. Thinking is particularly the characteristic of the scientist. For him, visible things are the symbol of a reality that can be thought but not seen. By using visible symbols, science provides a bridge from the visible to the intelligible world. Plato believed that thinking gives us knowledge of truth.