Plato (428 – 348 BCE) was an ancient Greek philosopher and student of Socrates. He is responsible for writing down many of Socrate’s teachings, which allows us in the modern day to reference them. He is also the teacher of Aristotle.
Theory of Forms
Plato is famous for his Theory of Forms (or Ideas). The theory is that all of reality first exists in a perfect form that is innately understood by all humans. The reality we experience are all downstream imperfect projections of this perfect form. Therefore, the reason we recognize an apple is an apple is because we innately understand what the idea of an apple is already. You may hear evidence of his influence in the idea of a “platonic ideal”.
This separation of the idea of an object from the material version of it is also the basis of Dualism, which, very generally, is the separation of material from the immaterial.