We have been using the lower case letters <math>p, q, r\!</math> for the basic propositions of abstract type <math>\mathbb{B}^3 \to \mathbb{B}</math> and the upper case letters <math>P, Q, R\!</math> for the basic regions of the universe of discourse where <math>p, q, r,\!</math> respectively, hold true. | We have been using the lower case letters <math>p, q, r\!</math> for the basic propositions of abstract type <math>\mathbb{B}^3 \to \mathbb{B}</math> and the upper case letters <math>P, Q, R\!</math> for the basic regions of the universe of discourse where <math>p, q, r,\!</math> respectively, hold true. |