Plato’s Doctrine of the Forms is central to his epistemology and metaphysics, because they ground both knowledge and being. Recall that Plato considers essences as real entities. A real thing that is the essence of goodness, and is called the Form of Goodness, exists. The same is true of justice, humanity, and other important essences. These things exist in an intellectual realm sometimes referred to as Platonic Heaven (because it is analogous in many ways to the Christian heaven — e.g., it has no physical location.) Everything that is good is good because it has some relation to the Form of Goodness.
It may seem strange to think that there is a Form of Goodness that is everywhere/nowhere in Platonic Heaven. But let’s consider 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 something is dropped, we expect it to fall. It always has, always does, always will.
Belief in the law of gravity is a standard, everyday belief. But if you replace “law of gravity” with “Form of Justice,” you may begin to realize that, just as there is something that makes dropped objects fall, there is something that makes a just act just. This "something" is the Platonic Form.
Perhaps an even clearer example is provided by numbers and mathematical entities.
What makes the truths of mathematics true? Considering all of the things that have been accomplished with applied mathematics, it would be strange to claim that “the fact that two plus two is four is true because concepts such as ‘two’ and ‘four’ are human inventions. They are completely dependent on the human mind, human language and how we have chosen to designate things.”
Instead, most of us believe that the laws of mathematics were true even before humans existed, that the number two is a genuine entity of some sort that has an independent reality, perhaps as a Platonic Form. (Note that many mathematicians identify themselves as Platonists with respect to numbers, and make this claim about numbers.) It can be helpful to consider mathematics in this way when attempting to understand Forms and Platonic Heaven. Plato developed a theory of mathematical Forms later in his life.
Why believe that there entities? Plato proposed that they must exist in order for knowledge to be possible. In the Cratylus, he argued as follows:
“Nor can we reasonably say, Cratylus, that there is knowledge at all, if everything is in a state of transition and there is nothing abiding; for knowledge too cannot continue to be knowledge unless continuing always to abide and exist. But if the very nature of knowledge changes, at the time when the change occurs there will be no knowledge; and if the transition is always going on, there will always be no knowledge, and, according to this view, there will be no one to know and nothing to be known: but if that which knows and that which is known exists ever, and the beautiful and the good and every other thing also exist, then I do not think that they can resemble a process or flux….”
Plato agreed with Heraclitus that the world we encounter through our senses is in flux (in fact, Plato cited Heraclitus when he made this point in the dialogue). However, if this applies to everything, then knowledge is not possible. If every human is always changing, and humanity itself is changing, how can claims that “Bob is human,” or “Bruiser is not human” be true?
Since we can attain knowledge, it must be true that not everything is in flux. However, since the world of the senses is in flux as Heraclitus described, it follows that what is not in flux cannot be of this world, but must belong to a metaphysical world, a world behind the world, a Platonic Heaven of essences. Plato accepted Heraclitian Flux, but only in the world of the senses. Platonic Heaven, like the world posited by Parmenides, is eternal and unchanging.
If we were to construct an argument about this, it would be as follows:
|The world of experience is in flux.||Premise/Factual Claim|
|If everything were in flux, knowledge wouldn't be possible.||Premise/Factual Claim|
|Knowledge is possible.||Premise/Factual Claim|
|Therefore, something outside our experience is not in flux.||Conclusion|
As we’ve discussed so far, 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 paradigms or ideals.
The analogous relationship between mathematical objects and Forms can help us to understand what Forms are like. Consider a circle. In all of the world, is there a perfect circle? The answer is “no.” If we examined the most precisely-drawn circles with a sufficiently-powerful microscope, we would find that their curves are not perfectly smooth. Also, we know that space itself curves slightly so, therefore, no Euclidian shape exists in the world (i.e., the world of the senses). There are no perfect circles in the world. However, there is perfection in Platonic Heaven. The Form of Circle is perfectly circular, and serves as the exemplar for all worldly circles.
What then, is the relation between the Form of Circle and worldly, imperfect circles? Plato’s answer is “participation.” Worldly circles participate in the Form of Circle just as humans participate in the Form of Human. But what does participation mean?
As indicated above, participation is grounding in 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 beyond those accounts of essences by assigning a cause-and-effect relationship. For example, the Form of Human is the cause of Bob, as a human. Bob only exists as a human because of the Platonic Form. This relation is also one of imitation. The worldly human imitates the ideal 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 more genuine, more real Form of Human.|
These are complex concepts. As a result, they have been involved in many interpretive challenges and scholarly disputes. For example, Plato insisted 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; the Form of Equality). However, some of Plato’s works seem to establish a Form any time there is a universal (e.g., a Form of Wheel or Taco), which has some undesirable consequences. There are also logical problems (e.g., Forms participating in other Forms).
This does not mean that Plato’s system is indefensible or broken. However, It is not possible to consider all of the details involved in this issue in this introductory course. We must be satisfied with acquiring an understanding of the general concepts.