  When writing the De Interpretatione, Aristotle had worked out the following theory of simple sentences: a (declarative) sentence (apophantikos logos) or declaration (apophansis) is delimited from other pieces of discourse like prayer, command and question by its having a truth-value. The truth-bearers that feature in Aristotle’s logic are thus linguistic items. They are spoken sentences that directly signify thoughts (shared by all humans) and through these, indirectly, things. Written sentences in turn signify spoken ones. (Simple) sentences are constructed from two signifying expressions which stand in subject-predicate relation to each other: a name and a verb (‘Callias walks’) or two names connected by the copula ‘is’, which co-signifies the connection (‘Pleasure is good’) (Int. 3). Names are either singular terms or common nouns (An. Pr. I 27). Both can be empty (Cat. 10, Int. 1). Singular terms can only take subject position. Verbs co-signify time. A name-verb sentence can be rephrased with the copula (‘Callias is (a) walking (thing)’) (Int. 12). As to their quality, a (declarative) sentence is either an affirmation or a negation, depending on whether it affirms or negates its predicate of its subject. The negation particle in a negation has wide scope (Cat. 10). Aristotle defined truth separately for affirmations and negations: An affirmation is true if it says of that which is that it is; a negation is true if it says of that which is not that it is not (Met. Γ.7 1011b25ff). These formulations, or in any case their Greek counterparts, can be interpreted as expressing either a correspondence or a deflationist conception of truth. Either way, truth is a property that belongs to a sentence at a given time. As to their quantity, sentences are singular, universal, particular or indefinite. Thus Aristotle obtains eight types of sentences, which are later dubbed ‘categorical sentences’. The following are examples, paired by quality: