Plato considered what the perfect or most ideal version of something could be. He concluded that all things we can conceive of in the world have their ideal antecedents in perfect “Forms,” and that these Forms act as guides or blueprints for our own understanding. But where do these Forms come from and how do we experience them? According to Plato, there is a realm where these ideal Forms exist that transcends time and space. This realm contains all the perfect examples of things: the most perfect circle, the most perfect chair, table, even the most perfect friendship. These Forms, and the realm they exist in, are abstract, but real nonetheless; unchanging, and absolute. It is in the image of these abstract Forms that God created the physical world, so what we experience in the empirical world is a mere, imperfect copy. And yet, we recognize these copies because we know the ideal Form “which can only be seen with the eye of the mind” (Plato, 375 c. BCE [2021] Plato: The Complete Works). Even though these Forms cannot be empirically experienced, our eternal soul, before we were given a physical entity, experienced them. This is what allows us to recognize objects in the world, in their imperfect, plural state. So, for Plato, there are objects in the world that are “always in a state of change. And these you can touch and see and perceive with the senses” while the “unchanging things you can only perceive with the mind” (Plato, 375 c. BCE [2021]).
One of the ways in which Plato illustrates this relationship between our empirical experience and the non-physical realm of ideals is through the allegory of the cave. Plato asks us to imagine prisoners who have lived in a cave for their whole lives. They are bound, unable to move, looking only at the cave wall. Behind the prisoners, there is a blazing fire. People holding a series of objects pass before this fire, casting shadows on the wall that the prisoners face. For the prisoners, those shadows make up the whole of their reality, even though a whole world lies beyond the cave. Plato uses this allegory to examine the journey from ignorance to enlightenment; when one prisoner is freed and journeys into the true reality beyond the cave, this mirrors the philosophical journey we undertake when we look beyond the illusory shadows of our own sensory experience to consider the perfect Forms.
Plato’s idealism explains our experience in a way that prioritizes a conceptual realm; where true, universal reality can only be accessed in the mind as ideas. This serves to demonstrate the way that idealism can be metaphysical/ontological without subscribing to the extreme immaterialism advocated by philosophers such as Berkeley. Plato still believed in a physical reality, even if he only regarded it as an imperfect copy of the world of Forms. True reality — this realm of Forms — is primarily conceptual, apprehended in the mind, but the empirical world still exists just as the shadows on the cave wall exist.
Kant’s transcendental idealism
We have seen, so far, the way in which idealism considers reality to exist most fundamentally in the mind, experienced only by the mind’s eye. In reference to ontological idealism, Farris and Göcke explain a slightly different idealistic approach,