Many people associate Plato with a few central doctrines that are advocated in his writings: The world that appears to our senses is in some way defective and filled with error, but there is a more real and perfect realm, populated by entities (called “forms” or “ideas”) that are eternal, changeless, and in some sense paradigmatic for the structure and character of the world presented to our senses. Among the most important of these abstract objects (as they are now called, because they are not located in space or time) are goodness, beauty, equality, bigness, likeness, unity, being, sameness, difference, change, and changelessness.
(These terms—“goodness”, “beauty”, and so on—are often capitalized by those who write about Plato, in order to call attention to their exalted status; similarly for “Forms” and “Ideas. ”) The most fundamental distinction in Plato’s philosophy is between the many observable objects that appear beautiful (good, just, unified, equal, big) and the one object that is what beauty (goodness, justice, unity) really is, from which those many beautiful (good, just, unified, equal, big) things receive their names and their corresponding characteristics.
Nearly every major work of Plato is, in some way, devoted to or dependent on this distinction. Many of them explore the ethical and practical consequences of conceiving of reality in this bifurcated way. We are urged to transform our values by taking to heart the greater reality of the forms and the defectiveness of the corporeal world. We must recognize that the soul is a different sort of object from the body—so much so that it does not depend on the existence of the body for its functioning, and can in fact grasp the nature of the forms far more easily when it is not encumbered by its attachment to anything corporeal.
In a few of Plato’s works, we are told that the soul always retains the ability to recollect what it once grasped of the forms, when it was disembodied prior to its possessor’s birth (see especially Meno), and that the lives we lead are to some extent a punishment or reward for choices we made in a previous existence (see especially the final pages of Republic).
But in many of Plato’s writings, it is asserted or assumed that true philosophers—those who recognize how important it is to distinguish the one (the one thing that goodness is, or virtue is, or courage is) from the many (the many things that are called good or virtuous or courageous )—are in a position to become ethically superior to unenlightened human beings, because of the greater degree of insight they can acquire. To understand which things are good and why they are good (and if we are not interested in such questions, how can we become good? ), we must investigate the form of good.