plato and aristotle on cosmology and epistemology
Plato and Aristotle lived around the same time (IV century B.C.) and Aristotle even studied at Plato’s Academy, yet surprisingly that did not mean they shared beliefs about the world around us. In fact, Aristotle was quite different (if not opposite in some areas) from Plato.
In particular, there were two areas where they disagreed and these were beliefs of where do we get the knowledge and how this universe works.
As Plato believed and taught, the world is divided into two realities – one of them “spiritual,” the reality of ideas or ideal forms and the other one is material, the world we see. In his famous Allegory of the Cave, he described the physical world’s objects as shadows of the ideal forms from the “outside.” He taught that most people are chained in the cave without the ability to turn their heads and see the real world. However, philosophers’ task was to transcend the captivity of the chains and become enlightened. This is one of the reasons why Plato believed that philosophers should be rulers – they could glimpse the way things truly were. Also, Plato believed in the immortality of a human soul.
Aristotle, on the other hand, believed that this physical world is all you get. He, like Plato, distinguished the world into two parts – substance and essence – but he said both of them are present in the world we see, the material (substance) of a thing is not separate from its essence. His universe was, in a manner of speaking, “what you see is what you get.” To take this a bit further, his views differed from Plato’s because while latter believed in one form and many “shadows” (for example, one perfect idea of a cat and many breeds of cats alive in our world), for former the thing contained the idea. And since there was no world of ideas, there was no place left for the soul’s immortality in his teaching as a result.
Why is the immortality of the soul important in given context? Because it sheds light on the epistemology of these two great thinkers.
Plato, who said the soul continues to exist in the “spiritual” world, taught that we get all our knowledge from the very beginning of our life, (or, rather, before we were even born), a priori. We are born with it because the soul we get already knows all these things. However, at the moment of our birth, we forget everything we know and have to study to recollect it. This would explain the phenomenon of children who possess deep knowledge and understanding at the very young age (even if this does not answer the question of why most of us have to input a lot more effort in studying for exams).
Aristotle was against this idea. He professed the belief that we are born with zero knowledge and have to gain it all on our own, through our own personal experiences, a posteriori. For example, when a child first encounters books for the first time, he has no idea what that thing is. When he sees other books, he can notice similar characteristics about the books that define them. Without even a conscious effort, the child will assign categories to these things, for example. He can make conclusions about its substance, for example (made out of paper or something else he encountered before), or that it has pictures inside and other yet-unknown-to-him flourishes. Finally, as he learns to read, he can distinguish between letters and languages.
These two great philosophers have definitely impacted the worldview of people in those days and even today, 2,400 years later, we still use the ideas and methods invented by them. Whether we gain the knowledge ourselves or we “recollect” it, it is obvious that Plato and Aristotle were on the right track, at least in some areas, and Christian theology is in debt to these thinkers.