... They are not streets rained upon.
Hypothetical Syllogisms are thus reducible, by merely grammatical change[2], or by the statement of self-evident implications, to the Categorical form. And, similarly, any Categorical Syllogism may be reduced to the Hypothetical form. Thus:—
All men are mortal.
Socrates is a man.
... Socrates is mortal.
This argument is not different, except in the expression of the Major and the Conclusion, from the following:—
If Socrates is a man, death will overtake him.
Socrates is a man.
... Death will overtake him.
The advantage of the Hypothetical form in argument is that it is simpler. It was much used in Mediæval Disputation, and is still more popular than the Categorical Syllogism. Perhaps the prominence given to Hypothetical Syllogisms as syllogisms in Post-Renaissance text-books is due to the use of them in the formal disputations of graduands in the Universities. It was the custom for the Disputant to expound his argument in this form:—