35. Second Classification of Propositions: According to Their Form. -- Form here means the union of subject and predicate as it is effected in the enunciation of the judgment.

(1) The proposition is affirmative or negative^{1} accordingly as the mind asserts that the predicate belongs to the subject, and consequently must be joined to it (compositio), or not (divisio).^{2}

(2) With the form of judgments must be connected their modality, or the particular determination which marks the union of predicate and subject. Under this aspect the proposition is apodictic, empiric, problematic. "Every proposition consists in asserting that [something] is contained in, or is necessarily contained in [something] else, or that it may happen to be contained."^{3}

The apodictic proposition (which we must take care not to confound with the proposition in necessary matter) asserts that the predicate necessarily agrees with the subject or is necessarily repugnant to it. As: There must be a First Cause in the world. It is impossible for the world to exist of itself.

The empiric proposition asserts that the predicate as a matter of fact agrees with the subject. As: So and so died yesterday morning.

The problematic proposition, based upon a mere possibility,^{4} asserts in a conjectural way the happening or non-happening of an event which has no natural connection with a determinate cause As: It is possible that so and so may draw the prize.

{1} A negative proposition sometimes has the appearance of an affirmative, as: This man lacks generosity -- is not generous. Inversely, an apparently negative proposition may be at bottom affirmative, as: Man is not infallible; The world is not infinite.

{2} Every proposition which asserts something (P) about a subject (S) mentally effects a certain union (composito) of a predicate with a subject. Here the belonging or non-belonging in question of the predicate and subject is objective. St. Thomas, Periherm., lect. 3.

{3} Prior Analyt., I, 2.

{4} For Aristotle possible here does not mean non-contradictory, but contingent. St. Thomas writes in the same sense: "That is called necessary which in its own nature is determined only to being; impossible that which is determined only to non-being; possible, that which is altogether determined to neither, whether it be more inclined to the one than to the other, or whether it be equally inclined to both, or, as it is expressed in differently contingent [ contingens ad utrumlibet ] ." In Periherm., lect. 14, n. 8.