The expression "not not p" is a logical statement that can be simplified. In logic, "not" negates a proposition. Therefore, "not not p" effectively cancels out the negation, resulting in the original proposition "p." This means that if "p" is true, then "not not p" is also true. This concept is often used in formal logic and philosophy to illustrate the principle of double negation. In classical logic, double negation is a valid rule, meaning that negating a negation returns you to the original statement. This principle is foundational in understanding logical reasoning and truth values in systems like Boolean algebra and propositional logic.