We know that propositional logic is not powerful enough to express all true statements, otherwise we wouldn't need predicate logic. It turns out that No logical system can be powerful enough to express all true statements.
Every system of logic has some notion of models for expressions.
A model for a collection of expressions is an interpretation that makes the expressions true. There are four possible truth assignments for the variables p and q. The following table shows the value of the two expressions for each assignment. The first and last assignments in the table make both expressions TRUE so they are the only two models for our set of two expressions. Recall that an interpretation for a predicate logic expression is a domain for the variables and definitions for each predicate. Entailment and proof are related but they are not the same.