Definition.com
Immanuel Kant is one for whom 'discovery' went thus.: any property that a real x had, an imaginary x could have, and any property that an imaginary x could have, a real x could have. So Existence is not a property. (Hearty applause, maintained steadily for 200 years so far.).
Definition.com
Plato's discovery went as follows: it is possible for something to be a certain way and for something else to be the same way. Thus, there are universals. (Tumultuous applause, which lasts, despite occasional subsidences, 2,400 years.) 'Universals' is simply the name philosophers give to the ways in which two or more things can be the same.
Definition.com
The Universal is simply the name philosophers give to the ways in which two or more things can be the same.
