The Concept of Belief One concept which continually recurs in the discussions of truth and knowledge is that of belief . We need to make two points about beliefs. The latter is the name of a proposition. What it is to believe that something is true is to believe that a certain proposition is true. Philosophers use the term 'belief' broadly.
Every proposition is true or false.
No proposition is both true and false. It was Tarski's special genius or insight to realize that a theory of truth is distinct from a theory of knowledge . The semantic theory of truth. The theory of Objective truth. It's worth spending a few further moments on this example.