What is it that makes something a 'Universal Truth?' A description with an example may help.
In argument an a priori assumption. A principle which is held to be true without proof. A oft used example is, "The killing of an innocent person is always wrong." Another is the assumption of existence, why the , "This is all a computer simulation" argument is always fun. Can't prove existence or non-existence.
The point is without these assumptions you cant get anywhere - can go anywhere actually - because you can prove (in the philosophical sense) nothing without establishing a starting point..
The key elements in human thinking are not numbers but labels of fuzzy sets. -- L. Zadeh
