Diaphorotes

(Disclaimer: This is a summary and sometimes concepts can be so summarized that they are wrong. Also, I have never studied philosophy in English so I might use some terms the wrong way.)

One of the things that Plato wanted to understand was how the human mind classifies objects:

For example: how is it possible that we can understand that two different looking dogs are part of the same category called "dog"?

Let's think about the definition of a dog: an animal with four legs, fur, a tail, two ears...

But two dogs can have two different colours of fur, a longer or shorter tail, or one of the dogs can be missing a leg.

Yet our mind will immediately tell us “oh look at these two dogs!”.

Let's think back to the definition of dog that I wrote earlier; we could also apply that definition to a cat. After all, a cat also has: four legs, hair, a tail, two ears, etc.

Yet our mind is capable of understanding instantly which of the two animals we have in front of us.

Although the same type of object can present itself in different ways (different color, shape, size, etc.), our mind will place it in the right category even though we have never seen - and learned- that particular shape of the object before .

To explain this, Plato created the theory of Forms (or theory of Ideas).

According to Plato there is a place called the world of Forms (Hyperuranion) in which all the perfect models (Form) of every object reside.

This place is beyond our world and everything that exists here is just a poor copy of the perfect Form that exists there.

So despite the fact that a dog can present itself in different ways, our mind can categorise the object perfectly because we can obtain the knowledge of its perfect Form from the Hyperuranion.

Lastly, how can we distinguish a cat from a dog according to this theory? An object similar to another? Every object has a peculiarity that makes it unique, a particular sign that differentiates it from all other things and defines it.