Socrates claims that all learning is recollection. He points out that we can be reminded of one thing by being made conscious of another thing. Socrates supports his theory by drawing on the Theory of Forms (see a brief description in the context of another Core Idea here) and Equality (something that is independent of any particular case of equality, such as equal sticks or equal stones). We know the Form of Equality, because it comes into our minds every time we see instances of equal objects. If the equal things are different from Equality and yet can bring Equality into our minds, they must somehow reminds us of the Form of Equality. We are aware that sticks or stones fall short of being perfectly equal, but to be aware that they fall short, we must already have an idea of what it means to be perfectly equal; that is, we must already know the Form of Equality.

There are no instances of perfect equality in the sensible world, and yet we have had this notion of Equality as long as we have been alive. Socrates infers that we cannot have come to learn of Equality through our senses, but that we obtained our knowledge of it before our birth. And if this holds true of Equality, it should hold true of all the other Forms as well. It would seem that we lose knowledge of these Forms at birth, and it is through a process of learning that we come to recollect them and know them again. This is why Socrates claims that all learning is recollection. 

Popular pages: Phaedo