1. Subject
2. Predicate
3. Copula
Quality and quantity
Quality refers to whether the proposition affirms or denies the inclusion of a subject within the class of the predicate. The two possible qualities are called affirmative and negative.[3] For instance, the A-proposition ("All S are P") is affirmative since it states that the subject is contained within the predicate. On the other hand, the O-proposition ("Some S are not P") is negative since it excludes the subject from the predicate.
Quantity refers to the amount of members of the subject class that are used in the proposition. If the proposition refers to all members of the subject class, it is universal. If the proposition does not employ all members of the subject class, it is particular. For instance, the I-proposition ("Some S are P") is particular since it only refers to some of the members of the subject class. Name | Statement | Quantity | Quality | A | All S are P. | universal | affirmative | E | No S are P. | universal | negative | I | Some S are P. | particular | affirmative | O | Some S are not P. | particular | negative |
An important consideration is the definition of the word some. In logic, some refers to "one or more", which could mean "all". Therefore, the statement "Some S are P" does not guarantee that the statement "Some S are not P" is also true.
In philosophy and logic, the term proposition refers to either (a) the "content" or "meaning" of a meaningful declarative sentence or (b) the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence. The meaning of a proposition includes having the quality or property of being either true or false, and as such propositions are claimed to be truthbearers.[citation needed]
The existence of propositions in sense (a) above, as well as the existence of "meanings," is disputed by some philosophers. Where the concept of a "meaning" is admitted, its nature is controversial. In