4. TWO KINDS OF HYPOTHETICAL ARGUMENTS.
The two kinds of hypothetical syllogisms are the constructive and destructive.
A constructive hypothetical syllogism is one in which the minor premise affirms the antecedent.
A destructive hypothetical syllogism is one in which the minor premise denies the consequent.
The constructive hypothetical is sometimes referred to as the “modus ponens”; whereas the destructive hypothetical is called the “modus tollens.”
ILLUSTRATIONS:
| Constructive Hypothetical Syllogisms. | |
| Symbols. | Words. |
| If A is B, C is D | If you are diligent, you will succeed; |
| A is B | And you are diligent, |
| ∴ C is D | Therefore you will succeed. |
| Destructive Hypothetical Syllogisms. | |
| If A is B, C is D | If you had been diligent, you would have succeeded; |
| C is not D | But you did not succeed, |
| ∴ A is not B | Therefore you were not diligent. |