Been working, all day, on a paper about Universals. I have been examinig the following argument which is made by at least 2 relatively unknown medieval philosophers, and, a similar argument by Albert the Great. It looks like this:
1. There is no scientific knowledge of non-existing things.
2. All scientific knowledge is of universals.
3. Therefore universals are existing things.
I think that a better argument, which would prove essentially the same thing, would be.
1. All scientific knowledge is of universals.
2. Universals do not exist.
3. Therefore all scientific knowledge is of things that do not exist.
Therefore, either 2 is wrong or 1 is wrong.
Scientific Knowledge is certain knowledge based upon rational inference (valid inductive or deductive syllogistic demonstrations - see Aquinas's commentary on Aristotle's Posteriora Analytica.). All demonstration begin with universals.( see Aristole's Priora Analytica) Therefore 1 is true. Therefore either 2 is false or all scientific knowledge is of non-existent things.
This, of course, does not say anything about HOW universals exist.