In ordinary English, the sentence "Fish swim." has a subject, "Fish", and a verb "swim". The verb, as defined by English grammar, is also called a "predicate." This is the simplest type of predicate, but, in general, a predicate can be understood as one or more words that say something about a subject. Thus, a predicate is attributive. In the sentence "John is tall", the predicate is "is tall". This predicate attributes tallness to John. In mathematical logic, the word "predicate" retains its English language sense of attributing some feature to a subject, but as we shall see, what is regarded as a predicate in the grammatical sense may not always be considered a predicate in the logical sense. Modern symbolic logic is generally broken into two parts: propositional logic (also called the propositional calculus) and predicate logic (also called the predicate calculus). Propositional logic is concerned only...