In mathematics we always assume that our propositions are definite and unambiguous, so that such propositions are always true or false (there is no intermediate option). In this respect they differ from propositions in ordinary life, which are often ambiguous or indeterminate. We also assume that our mathematical propositions are objective, so that they are determinately true or determinately false independently of our knowing which of these alternatives holds. We will denote propositions by capital Roman letters.