Mathematics without infinitely small, continuous mathematical objects. The mathematics of finite sets. Propositional calculus Comes from the linguistic concept that things can be either true or false. We should avoid variables when forming statements, as they may change the logical value. 2=7 statement x=5 not a statement In logic we do not use the equals sign, we use the equivalence sign \equiv. Logical values (booleans) are denoted by either 0 or 1 (or t, f, etc.