Understanding Key Concepts in Plato's Philosophy

Justice: Under a general, stable, and perfect order of a whole, justice exists in the individual soul or the state, where the parts perform their specific function in an appropriate manner and according to their deserved power.

The Good: Plato's idea of the Good is the first of the ideas in dignity and power, comparable to the sun. It is the cause of being and intelligibility of ideas, as well as our knowledge of them. The knowledge of the Good ends the dialectic and the formation of governing ideals.

Pleasure: Plato finds meaning in and reacts against sensual enjoyment of the body. According to Plato, not all pleasures are good or beneficial.

Intelligence: Used in the sense of intellectual activity in general. It is not enough to think and be smart; one must know and contemplate the idea of the Good for true wisdom, because without it, being smart is not worthwhile. True wisdom comes from knowing the Good.

Appearance: Appearance is what seems to be, but it is changing and changeable. It is of things. Appearances are changing, like the views or opinions of people. The big problem is the ease with which human beings are carried away by appearances.

Nature (physis): Refers to the origin of things and the stuff of which they are composed. It is outside the human will and unalterable.

Ignorance is folly and madness, as the prisoner of the cave not only has no real knowledge but has lost his mind.

Science is a form of knowledge that opposes opinion and is true knowledge. It is infallible because it is based on reasons for doing so.

Idea (Form): For Plato, simple ideas are not universal concepts drawn from experience. They are essences remaining independent of particular things or events.

Opinion (Doxa): A lower form of awareness than science, mere opinion. Opinion may be true or false, fallible and unstable because it is not based on solid grounds. Plato often said that the object of opinion is the physical world.

Virtue is the excellence of a being in general or a capacity, the excellence through which it acts perfectly and outstandingly. Each agent corresponds to a mode of being that makes it act. Plato usually lists five virtues: piety, justice, prudence, courage, and moderation.