Plato’s Theory of Forms and Its Significance Today

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The dichotomy between truth and appearance, and the devaluation of appearance, is rooted in pre-Socratic philosophy. Just as Plato leant upon Heraclitus’ flux for his conception of the sensible world of appearance (the world as we see it), so he leant upon Parmenides’ unity for his conception of the intelligible world (the world when we think it), which he rendered as the ideal, immutable realm of the Forms.

The Genesis of the Forms

Plato’s authorship spanned some fifty years, from the death of Socrates in 399 BCE to his own death in c. 348. He is traditionally ascribed with 35 dialogues, although around ten of these may be spurious. Today, the dialogues are often classified into three periods, early, middle, and late, based on their presumed order of composition.

The early dialogues are relatively short and accessible. They are sometimes referred to as the Socratic dialogues because they set forth more of the historical Socrates, typically debating ethical subjects such as temperance, courage, or friendship with youths, friends, or a supposed expert.

From these beginnings, Plato gradually developed distinct philosophical ideas, such as his Theory of Forms, which features in middle dialogues such as the Phaedo, Symposium, and Republic. In these long, literary dialogues, the character Socrates is less of the historical Socrates and more of a mouthpiece for Plato. He is accordingly more didactic, putting forth positive doctrines and no longer content merely to question and refute. Other middle dialogue doctrines that are unlikely to owe to Socrates include the Theory of Recollection, the Theory of Reincarnation, and the Theory of the Tripartite Soul—which are each connected to the Forms.

The Forms in the Phaedo

The Phaedo is named for the young Phaedo of Ellis, whom Socrates had rescued from slavery. For the first time, Plato explicitly appeals to the Forms, although does not do much to explain them. He also assumes reader familiarity with the Meno and the Theory of Recollection, which the Phaedo builds upon.

In the Phaedo, which used to be called On the Soul, Socrates offers four arguments for the immortality of the soul, among which the Theory of Recollection and the Theory of Forms. The supposed immortality of the soul enables Socrates to remain sanguine in the face of his pending execution, and offers the ultimate justification for the life of virtue. The dialogue ends with a myth of the afterlife and, of course, the dramatic drinking of the hemlock.

Socrates argues that that which is compounded is dissoluble, but that which is uncompounded is indissoluble and therefore unchanging. The Forms (for instance, Beauty), which are unchanging, are uncompounded, but their particulars (for instance, a beautiful horse), which are in a constant state of composition and degradation, are compounded. Particulars are apprehended by the senses, but the Forms can only be apprehended by the mind. Since the soul cannot be apprehended by the senses, it must be immortal.

The embodied soul employs the body as an instrument of perception, but what the body perceives is in a perpetual state of flux, so that the soul is thrown into confusion. But when the soul is once again detached from the body, or when it turns inward to contemplate itself, it passes into the realm of the unchanging and approaches wisdom.

Socrates affirms that the Theory of Forms is the most plausible theory of the deep causes of things. On this account, something is beautiful because it participates in the Form of Beauty, two is two because it participates in the Form of Duality, and so on. A thing that participates in a Form also participates in other closely related Forms. For instance, three bundled pencils participate in the Form of Oddness as well as the Form of Threeness. However, opposite Forms such as Even and Odd cannot admit of each other. Whenever a soul is embodied, there is invariably life, indicating that the soul is closely connected with life, and thus that it cannot admit of its opposite, death.

The Symposium: Love as the Engine of Wisdom

In the Symposium, Socrates relates the time when the priestess Diotima taught him the proper way to learn to love beauty. A youth should first be taught to love one beautiful body so that he comes to realize that this beautiful body shares beauty with every other beautiful body, and thus that it is foolish to love just one beautiful body. In loving all beautiful bodies, the youth begins to appreciate that the beauty of the soul is superior to the beauty of the body and begins to love those who are beautiful in soul regardless of whether they are also beautiful in body. Having transcended the physical, he gradually finds that beautiful practices and customs and the various branches of knowledge also share in a common beauty. Finally, on the highest rung of the ladder of love, he is able to experience Beauty itself, rather than its various apparitions. By exchanging the various apparitions of virtue for Virtue herself, he gains immortality and the love of the gods.

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The Republic: The Form of the Good

In Book 5 of the Republic, in discussing the ideal state and the education of its guardians, Plato introduces the elusive Form of the Good. It is by attaining the Form of the Good that the philosopher-king is made fit to rule. As the Form of the Good is impossible to describe, and difficult to imagine, Socrates tries to convey its essence through three interconnected metaphors: the famous sun, line, and cave, which I discuss in a separate article.

Legacy of the Forms

In the Phaedo, the Theory of Forms is presented as “the most plausible theory,” without any backing or questioning. In later dialogues, Plato becomes more doubtful—and in the Parmenides, has Parmenides demolish his pet Theory of Forms.

Arresting though it may be, the Theory of Forms is never definitive, and features less prominently in the late dialogues. Part of the pleasure and privilege, and seduction, of reading Plato is that he is thinking with us, rather than simply telling us what he thinks, or what to think.

In any case, our main interest in the Theory of Forms is not in its logic or coherence, but in its impact and influence. The Phaedo entrenched most of the divisions or dualities that mark the Western mind, including soul and body, mind and matter, reason and sense experience, reason and emotion, reality and appearance, good and evil, heaven and hell… In the Western tradition, since the Phaedo, the body is the source of all evil. But in the Eastern tradition, for instance, in yoga, we can take control of the mind through the body.

Although the Phaedo is at the root of Western psychology, philosophy, and theology, it is also deeply Eastern in advocating supreme detachment and ego suppression or disintegration as the route to salvation. Also, death is an illusion … we will be reincarnated … according to our deeds (karma). These, however, are not the aspects that the West has retained.

Read more in The Gang of Three: Socrates, Plato, Aristotle.