Plato's argument for the existence of the Forms revolves around the idea of our experiencing of objects and their associated properties. Plato argues that through our senses we experience particular things that we assign certain abstract concepts, their properties. However, we never experience these abstract concepts. Using the example of beauty, we may experience numerous things we would describe as beautiful and yet we never experience beauty. In seeing numerous examples of particular things we would say are beautiful we may note there is something they all share, beauty. Plato then argues that something must exist that is beauty, a universal, a property that can be possessed by more than one thing. This, Plato claims, is the Form of beauty that we never sense directly but is manifested in our experience through various things we describe as beautiful.
Plato aims to give greater grounding to his claim by arguing that the Forms exist independently of these things we experience. We may imagine a situation where we collect together all the beautiful things and destroy them in a great purge. However, this vast devastation would not destroy the concept of beauty itself. Beauty, Plato claims, would still exist as a concept to us and as such it must be some separate thing that possesses independent existence of these beautiful things. This argument applies generally across all the Forms and is used by Plato to establish the view that objects and things participate in the Forms but hold an independent existence from one another.
In conclusion, we may note that there are various abstract concepts that we never sense directly and yet we describe the objects of our perception as possessing properties that are, in effect, derivatives of these abstract concepts. These abstract concepts, via Plato's argument outlined above, possess some independent existence as the Forms with the things we experience participating in them.
