Used as checks.
(6) Mnemonic lines.
Their use explained.
Reduction.
(7) Relative value of the four figures.
9. SUMMARY.
(1) By a syllogistic figure is meant some particular arrangement of the three terms in the two premises.
This arrangement yields four figures which are designated by the position of the middle term.
To be logical, any syllogism must conform to one of the four figures. The first figure is suggested by the position of the terms of the “Socrates is mortal” syllogism. The second is derived by converting the major premise of the first; while the third figure results from converting the minor premise of the first, and the fourth by converting both major and minor of the first.
(2) By a mood of a syllogism is meant some particular arrangement of the propositions which compose it.