[Footnote 2:] When we speak of the Minor or the Major simply, the reference is to the terms. To avoid a confusion into which beginners are apt to stumble, and at the same time to emphasise the origin of the names, the Premisses might be spoken of at first as the Minor's Premiss and the Major's Premiss. It was only in the Middle Ages when the origin of the Syllogism had been forgotten, that the idea arose that the terms were called Major and Minor because they occurred in the Major and the Minor Premiss respectively.
Chapter II.
FIGURES AND MOODS OF THE SYLLOGISM.
I.—The First Figure.
The forms (technically called Moods, i.e., modes) of the First Figure are founded on the simplest relations with the Middle that will yield or that necessarily involve the disputed relation between the Extremes.
The simplest type is stated by Aristotle as follows: "When three terms are so related that the last (the Minor) is wholly in the Middle, and the Middle wholly either in or not in the first (the Major) there must be a perfect syllogism of the Extremes".[1]
When the Minor is partly in the Middle, the Syllogism holds equally good. Thus there are four possible ways in which two terms (ὅροι, plane enclosures) may be connected or disconnected through a third. They are usually represented by circles as being the neatest of figures, but any enclosing outline answers the purpose, and the rougher and more irregular it is the more truly will it represent the extension of a word.
| Conclusion A. All M is in P. All S is in M. All S is in P. | |
| Conclusion E. No M is in P. All S is in M. No S is in P. | |
| Conclusion I. All M is in P. Some S is in M. Some S is in P. | |
| Conclusion O. No M is in P. Some S is in M. Some S is not in P. |