A **mathematical proposition** is an assembly of symbols and letters formed by following certain rules, with the help of logical connectors.

In the calculation of propositions, the propositions used may not have a particular meaning. We can replace a proposition by “*Peter is mortal*” or “*Peter is a man*“, for example, and what interests the mathematician is the way that the basic propositions are then combined to construct reasoning.

The expression “**inverse proposition**” is the name given to the conditional Q → P in opposition to the proposition P → Q.

### Property

Mathematical logic dictates that all statements that do not contain a variable can only have one truth value: the statement is either true or false. It cannot be both true and false at the same time (principle of non-contradiction) and it cannot be neither true nor false (principle of excluded middle).