Plato's Hierarchy of Knowledge: Science Versus Opinion

Plato's Theory of Knowledge

Plato establishes two broad levels of knowledge in terms of the degrees of being. He distinguishes between knowledge of the sensible world, which he calls opinion, and understanding the world of ideas, which he calls science.

Distinctions within Knowledge

• Science: Within science, Plato distinguishes between intelligence (or dialectic), which understands the ideas and their hierarchical relationships, and mathematical thinking, which serves as a bridge between the two worlds and is responsible for knowledge of numbers, shapes, and mathematical/logical demonstrations.
• Opinion: In the realm of opinion, there are two levels: belief (knowledge of what is imaginable) and imagination (knowledge by images).

While science has a stable object, opinion has no stable object. Science is universal and necessary; it is knowledge of what cannot be otherwise. It causes and works from first principles.

Mathematical Thinking Process

1. It starts from physical models of ideal entities.
2. From these principles, axioms, postulates, and definitions are established and shown by inference.
3. Theorems are then shown by deduction from the above.

Plato was interested in mathematics because it serves as a bridge between the two worlds. It uses sensitive models of ideal entities and tends to direct the soul toward a necessary course of action, which will eventually be essential to achieve the degree known as Noesis.

The Path to Noesis

Noesis is the intuitive knowledge of the ideas in themselves, achieved through the method Plato calls dialectic.

Hierarchy and Dialectic in the World of Ideas

In the world of ideas, there is a hierarchy of genera and species. For Plato, the whole idea can be divided or united to form a larger one, which corresponds to the concepts of analysis and synthesis.

Taxonomy and Method

Any idea called a genus divides and results in a species. The dialectic method involves starting with a simple idea and climbing up to the Idea of the Good. Both in the ascent and descent, one must define the ideas being passed through. Completing this course results in an intellectual intuition of the ideas, which is the noesis—a clear and singular view.