Plato's Argument For The Existence Of Forms

The passage from 72e to 77a in Plato’s Phaedo contains Plato’s argument for the idea that the soul exists before birth. This argument relies heavily on Plato’s Theory of Forms. For Plato, the sensory, material world is full of impermanence, instability, contradiction, and illusion. Therefore, Plato says, for knowledge to be possible, there must be a realm of objects, namely “Forms”, which exist outside of the spatiotemporal realm, and which mediate our knowledge of the sensory world. These Forms are more real than objects in the sensory realm, and they are permanent, stable, unchanging. To argue for the existence of Forms, Plato gives an example of a piece of wood A, which is equal to another piece of wood, B, and which we understand as an instance of equality. However, he points out a third piece of wood, C, which A is unequal to. Therefore, even though A and B give us the idea of Equality, neither of them can
Since this knowledge cannot come from the senses (since no sensory objects are the Equal), it must come to us through some other avenue. Since we have always known of Equality, but we could never have learned it from some sensory experience, we must have been born with this knowledge, which implies that we knew of Equality, and the other forms, before we were born. This means that during our life, when we seem to be learning about the Forms, we are not actually acquiring this knowledge for the first time (since, as was shown, knowledge of Forms is not acquired through the senses); instead, what appears to be learning is a recollection of what we knew before our birth (75a-75c). All knowledge is present within oneself, and one can be guided towards the answer or a solution, but to truly learn something one needs to fully be able to understand the concept and relate it to previous knowledge or experience, and make that knowledge truly yours by grasping