This is a term usually used to refer to realism, the idea regarding the existence of universal and abstract objects. It is named after the Greek philosopher Plato – a student of Socrates.

Universals were ideal forms according to Plato. This stance is called Platonic idealism. Plato’s Forms include numbers and geometrical figures making them a theory in mathematical realism. Form of the good is also included making it a theory of ethical realism.

Universals do not exist In Platonic realism, the way that ordinary physical objects exist, even though Plato metaphorically referred to such object to explain his concepts.

More modern versions of the theory avoid applying potentially misleading descriptions to universals. Instead, such versions maintain that it is meaningless to apply the categories of space and time to universals. Regardless of their description,

Platonic realism holds that universals do exist in a broad, abstract sense, although not at any spatial or temporal distance from people’s bodies.

Thus, people cannot see or otherwise come into sensory contact with universals, but in order to conceive of universals, one must be able to conceive of these abstract forms.