Each figure is divided into moods, according to what are called the quantity and quality of the propositions, that is, according as they are universal or particular, affirmative or negative. The following are examples of all the legitimate moods, that is, all those in which the conclusion correctly follows from the premises. A is the minor term, C the major, B the middle term.
First Figure.
| All B is C | No B is C | All B is C | No B is C |
| All A is B | All A is B | Some A is B | Some A is B |
| therefore | therefore | therefore | therefore |
| All A is C | No A is C | Some A is C | Some A is not C |
Second Figure.
| No C is B | All C is B | No C is B | All C is B |
| All A is B | No A is B | Some A is B | Some A is not B |
| therefore | therefore | therefore | therefore |
| No A is C | No A is C | Some A is not C | Some A is not C |
Third Figure.
| All B is C | No B is C | Some B is C | All B is C | Some B is not C | No B is C |
| All B is A | All B is A | All B is A | Some B is A | All B is A | Some B is A |
| therefore | therefore | therefore | therefore | therefore | therefore |
| Some A is C | Some A is not C | Some A is C | Some A is C | Some A is not C | Some A is not C |
Fourth Figure.
| All C is B | All C is B | Some C is B | No C is B | No C is B |
| All B is A | No B is A | All B is A | All B is A | Some B is A |
| therefore | therefore | therefore | therefore | therefore |
| Some A is C | Some A is not C | Some A is C | Some A is not C | Some A is not C |
In these exemplars, or blank forms for making syllogisms, no place is assigned to singular propositions; not, of course, because such propositions are not used in ratiocination, but because, their predicate being affirmed or denied of the whole of the subject, they are ranked, for the purposes of the syllogism, with universal propositions. Thus, these two syllogisms—