Essentialism attempts to explain the real by asserting that for a thing to be real is to be the kind of thing that it is. To be a real horse is to simply be a horse. To be a real man is simply to be a man. In other words, to be real is to be an essence. Platonism, one of several forms of essentialism, ascribes full reality to the “forms” or “essences” in themselves. Full reality is found in “horse-ness,” “man-ness,” etc. “Horse-ness” and “man-ness” exist as essences, not just as individual horses and men. These transcendent, archetypal forms, however, are not immediately experienced. Instead, the things we experience ( this horse, this man, etc.) are real by virtue of their participation in the forms.
The difficulty, however, lies in explaining the relationship between the universal form and the particular thing. In other words, if the forms exist in themselves, then how can they be considered universals? Also, how can the form as a pure essence have an existence separate from the particular, yet at the same time be united to the particular in order to give reality to it? To put it another way, it seems that Plato’s “universals” actually exist as “particulars,” and if so, they cannot be that which gives reality to the particular.
Even if a platonist is somehow able to explain that relationship, however, essentialism still fails to explain what it means to be “real” for the simple reason that to know what something is (essence) is not to know that it is (existence). For example, one can know what a unicorn is, but that says nothing about if unicorns actually exist . Again, a one hundred dollar bill in my wallet and a one hundred dollar bill in my mind have the same exact “whatness.” But the one in my mind has no purchasing power because it is not properly real.
In sum, because we cannot know that a thing is simply by knowing what a thing is, platonism provides no adequate answer to the most fundamental question of metaphysics, “What does it mean to be real?”