Informally, the truth value 1 represents full truth and the truth value 0 represents full falsity; intermediate truth values represent intermediate degrees of truth. Thus a formula is considered fully true under an evaluation "e" if "e"("A") = 1. A formula "A" is said to be "valid" in an MTL-algebra "L" if it is fully true under all evaluations in "L", that is, if "e"("A") = 1 for all evaluations "e" in "L". Some formulae (for instance, "p" → "p") are valid in any MTL-algebra; these are called "tautologies" of MTL.