Plato's Theory of Knowledge

The problem of reality and the problem of knowledge are intimately related; it is not possible to separate them. Plato argues that true knowledge must possess characteristics of objectivity and universality.

In his attempt to find the concepts or definitions of virtue as a basis for moral practice, Plato realized that the objects of sense perception are constantly changing (in a state of flux), and therefore these objects cannot be given a definition valid for all time. For this reason, science cannot be reduced to sensation, because science is objective, infallible, and universal knowledge. Plato does not accept that absolutely everything is subject to becoming, as the essence of things, i.e., the universal concept, escapes becoming.

Only the latter [the universal concept] can be the object of science, because only it is stable and capable of a universally valid definition. Now, the essence, i.e., the Universal, Plato identifies with the Ideas or Forms. Therefore, the Ideas are the basis for the objectivity and universality of knowledge.

The Role of Hypothesis

For Plato, a hypothesis is something assumed as a starting point, upon which something else depends, and which can only be grasped by thought. It is assumed to be primary in order to proceed to something else. In general usage, a hypothesis is a provisionally accepted proposal. However, in Platonic ontology (the science of Being qua Being), a hypothesis refers to a foundational being, specifically an Idea.

This concept of a foundational Idea or hypothesis applies not only to the relationship between different levels of reality but also to the relationship between Ideas themselves. It is also discussed that some Ideas are subordinate to others in a hierarchical fashion, reaching the highest, the Good, which encompasses all other Ideas and is therefore foundational.

Levels of Knowledge: Doxa and Episteme

For Plato, knowledge is divided into two levels: Doxa and Episteme. Each corresponds to one of the realms. Because each belongs to a different realm, each level of knowledge concerns different objects: Doxa concerns appearances, and Episteme concerns Ideas.

In turn, each of these levels is divided into two grades of knowledge:

• Doxa (Opinion): Imagination and Belief
• Episteme (Science): Thought and Intelligence