Central to all of Plato’s philosophy is his Doctrine of the Forms (or Ideas — note the use of capitalization). Forms are the basis of his metaphysics and epistemology, because they are the grounds for all truth. Recall that Plato was interested in concepts, not only as terminology, but metaphysically. He wanted to understand how they exist in reality, their essences.
Plato’s notion of essences is connected to his epistemology, and is the way in which knowledge becomes possible. Recall that, in Plato's philosophy, knowledge is justified true belief. This definition (or an approximation of it) is still used and defended 2,400 years later.
How can we justify a belief? Recall the examples provided in the previous tutorial, which involved guessing the number of fingers held up behind someone's back: seeing the fingers reflected in a mirror, being signaled by a friend, observing patterns, etc. What all had in common was that they were somehow grounded in the world. Justification is tied to seeing the world as it is, to properly relating a belief to the world as it exists. When you properly connect a belief to the world as it is, your belief is justified.
Therefore, in order to justify a belief, one must access the world as it really is. For Plato, this meant that he must know the essence of things. If someone says, “I know that Jen is a human,” that person must know what a human is, what makes a human a human: its essence. This is generally true of essences, but Plato held a nuanced (and influential) view of essences, his doctrine of the Forms or Ideas (i.e., the Platonic Forms — note how capitalization is used when referring to Plato’s concepts).
In Plato's philosophy, essences are real entities. A real thing exists that is the essence of goodness: it called the Form of Goodness. The same is true of Justice, Humanity, and other important essences. The essences of these things do not exist in the world, but in an intellectual realm sometimes called Platonic Heaven (because it is, in some ways analogous to the Christian heaven — e.g., it has no physical location). Everything that is good is good because it has some relation to this essence, the Form of Goodness.
It may seem strange that there is a Form of Goodness that is everywhere/nowhere in Platonic Heaven. Let's consider an example that involves something more familiar. Do you believe in the law of gravity? If so, where is it? Everywhere? Nowhere? Platonic Heaven? All we know is that, when an object is dropped, it falls. If you replace “law of gravity” with “Form of Goodness,” Plato's concept may begin to seem less strange to you. Just as there is something that makes objects fall when we remove support from them (e.g., when we drop them), there is something that makes a good act good. This is the Platonic Form.
If there are such entities as Forms, they must play an important role in our theory of knowledge. Let's return to the law-of-gravity analogy. If we can accurately describe the law of gravity, then we can also know the way an object behaves when it is dropped. If we know the law of gravity, then we are justified in our belief about what will happen when an object is dropped. Similarly, if we can describe the Form of Justice accurately, we can be justified believing that a particular act, policy, or government is just or unjust. If we know the Form of Humanity, then we can be justified in a belief as to whether someone is or is not a human being (and what makes a good human being.)
Since Platonic Forms are the metaphysical grounding of reality, knowledge of reality is grounded in knowledge of the Forms. They are the entities through which all knowledge comes. If we can access them and know their true nature, then we are justified in any belief to which they apply.
Recall that it can be helpful to consider mathematical entities and the realm of mathematics when attempting to understand Forms and Platonic Heaven. Plato himself developed a theory of mathematical Forms later in his life.
Why should we believe that there are such entities as Forms? Plato maintained that Forms must exist in order for knowledge to be possible. In an important way, Plato agrees with Heraclitus that the world we encounter through our senses is constantly in flux. However, if this applied to everything, then knowledge would not be possible. If every human being is always changing, and humanity itself is changing, then how can claims that “Bob is human,” or “Bruiser is not human” be true?
Since we can have knowledge, not everything is in constant flux. Since the world of the senses is in flux (as Heraclitus indicated), what is not in flux cannot be of this world: it must belong, instead, to a metaphysical world, a world behind this world, a Platonic Heaven of essences. Plato adopted Heraclitan Flux, but only with respect to the world of the senses. Platonic Heaven, like the world posited by Parmenides, is eternal and unchanging.
As we’ve discussed, Forms are essences that exist as individual entities in an intellectual realm. But what are Forms like? What kind of things are they? Think of them as perfect objects: as ideals, or paradigms. For example, consider a circle. In all of the world, is there a perfect circle? The answer is no. Examination of the most-accurately drawn circles with a sufficiently-powerful microscope will reveal that their curves are not perfectly smooth. Furthermore, we know that space itself curves slightly. As a result, no flawless Euclidian shape exists in the world. In the world, there are no perfect circles. But perfection exists in Platonic Heaven. The Form of Circle — the essence of Circle — is perfectly circular, serving as an exemplar for circles in the world of the senses.
What is the relationship between the Form of Circle and worldly, imperfect circles? Plato’s answer was “participation.” Worldly circles participate in the Form of Circle, just as humans participate in the Form of Human. But what is participation? As indicated above, it is a grounding of truth. “Bob is human” is true, because Bob participates in the Form of Human. In this way, Plato’s Forms are similar to other philosophical accounts of essences. Plato, however, went further by assigning a cause-and-effect relationship. According to Plato, the Form of Human is the cause of Bob, as a human. Bob only exists as a human because of the Platonic Form. This relationship also involves imitation. The human in the world of the senses imitates the real Form of Human.
|Key Aspects of Participation include...||Example|
|...a grounding of truth||“Bob is human” is true because Bob participates in the Form of Human.|
|...a cause and effect relationship||The Form of Human is the cause of Bob, as a human.|
|...an exemplar||The worldly human imitates the real Form of Human.|
These are complex concepts and, therefore, there have been (and continue to be) interpretive challenges and scholarly disputes. For example, Plato maintained that there are mathematical Forms, ethical Forms (e.g., the Forms of Justice and Goodness), and logical and metaphysical Forms (e.g., the Form of Being and the Form of Equality). However, some of Plato’s works seem to indicate a Form any time there is a universal (e.g., a Form of Wheel or Taco). This can have undesirable consequences. Some logic issues are also involved, such as Forms participating in other Forms. This does not mean that Plato’s system is indefensible. It is not possible for us to consider all of the details of these disputes in this introductory course. We must be satisfied with acquiring a general understanding of these concepts.