 Proof and truth are defined by independent methods and it is not trivial, but necessary, to prove that they are extensionally the same. This is the content of the completeness theorem when this property is predicated of a sound calculus. There is another meaning of completeness, when it is predicate of a theory: A theory \(\Gamma\) is complete when for each sentence, either \(\varphi\) or \(\lnot \varphi\) is a consequence of \(\Gamma\) (Manzano 1989 [1999: 118]). Strong completeness of a calculus establishes its sufficiency for capturing the logical consequence; namely, whenever a sentence follows logically from a set of hypotheses, there is a proof of this sentence in the calculus, possibly using some of these hypotheses. In contrast, weak completeness says that we have proofs for all validities. In a  complete[8]  logic, the expressive power of the language and its computational strength are well balanced. Thus the question about completeness is the question about the equilibrium of the basic components of a logic: its semantics and its logical calculus.