Rational thinking (ie, logic) assumes something in order to deduce something. However, an assumption may also be a deduction and vice versa. So, if there is a final truth to deduce, is it then an assumption or a deduction? According to traditional empirical science it is neither, but according to belief (eg, particle physics and cladism) it is both.
The final truth is thus either nothing or a contradiction, and a contradiction can’t be real. It means that the final truth is nothing (if it is real).