# Calculability in Mathematical Logic: Understanding Truth and Falsehood

Calculability is a concept in mathematical logic and the foundations of mathematics that refers to the ability of a formal system to determine the truth or falsehood of a statement within that system. A statement is said to be calculable if it can be proven or disproven using the rules of the system.

In more detail, a statement is calculable if there exists an algorithm, or a set of steps, that can be applied to the statement to determine its truth or falsehood. This algorithm may involve the application of certain axioms, definitions, and other rules of the formal system, as well as the use of logical operators such as negation, conjunction, and disjunction.

For example, in propositional logic, the statement "Either A or B" is calculable because we can use the laws of logic to determine whether it is true or false. If we know that A is true, then the statement is true, and if we know that A is false, then the statement is false. In this case, we can use a truth table to determine the truth value of the statement.

In contrast, the statement "The set of all sets that do not contain themselves" is not calculable, because it is a self-referential paradox that cannot be resolved using the rules of any formal system. This statement is known as Russell's Paradox, and it highlights the limitations of naive set theory and the need for more sophisticated foundations for mathematics.

Overall, calculability is an important concept in mathematical logic and the foundations of mathematics, as it helps to determine which statements can be proven or disproven within a given formal system, and which statements are inherently undecidable.