EXISTENTIAL COMMITMENT

It might also seem that an A proposition (with the form “All S is P”) implies the corresponding I proposition (with the form “Some S is P”). This, how- ever, raises a difficult problem that logicians have not fully settled. Usually when we make a statement, we are talking about certain specific things. If someone claims that all whales are mammals, that person is talking about whales and mammals and stating a relationship between them. In making this statement, the person seems to be taking the existence of whales and mammals for granted. The remark seems to involve what logicians call exis- tential commitment to the things referred to in the subject and predicate terms. In the same way, stating an E proposition often seems to commit the speaker to the existence of things in the subject and predicate classes and, thus, to imply an O proposition. For example, someone who says, “No whales are fish” seems committed to “Some whales are not fish.”