5. SPECIAL CANONS RELATED.
After a particular mood has been tested in the regular way, it has been intimated that the student may refer to the tabulated list of valid moods to ascertain, with a certainty, the validity of his reasoning. This is equivalent to referring to the answers in arithmetic; for if the student is unable to find the mood in the figure in which he has proved it valid, then he knows that he has made some mistake in his reasoning. A second check, though not absolute, is to recall the special canons of section four. If, for example, our reasoning has led us to believe that A
E
E is valid in the first figure, we may recall that the minor premise of the first figure must be affirmative and therefore AEE cannot be valid.
A few suggestions relative to memorizing the special canons may not be out of place. The two canons of the first figure must be committed, and then it may be remembered that the second figure is the negative figure of logic. Other figures may yield a negative conclusion, but the second must yield a negative conclusion. Since a negative conclusion necessitates a negative premise, it follows that the second figure must always appear withone premise negative. The other canon which pertains to the major premise is the same as the “major premise” canon of the first figure.
The third figure is the particular figure of logic. Other figures may yield particular conclusions, but the third must do so. This helps us to remember the canon that the conclusion of the third figure must be particular. The other canon which relates to the minor premise is the same as the “minor premise” canon of the first figure. The canons of the fourth figure are in reality a summary of the canons of the other three figures.