1. Syllogisms
Basic Argumentation

3. Definition
A syllogism is two statements or propositions, one major and one minor, that combine to produce a conclusion.

4. Example #1
Major Proposition: Every automobile has a seat for its driver.
Minor Proposition: Baby strollers have no seats for drivers.
Conclusion: Baby strollers are not automobiles

5. Major and Minor
If both the major and minor propositions are true, and if they lead logically to the conclusion, then the syllogism is both VALID and TRUE.
But the word “valid” pertains only to the logic; it has nothing to do with whether the propositions are true. Some valid syllogisms may not be true.

6. Example #2 Major Proposition: All textbooks are yellow.
Minor Proposition:
I own several textbooks.
Conclusion: All of my textbooks are yellow.

7. Positive vs. Negative
Syllogisms can be trusted to be valid only when both propositions are positive
Negative syllogisms usually do not work because they do not contain common elements on which to build a conclusion—even if both propositions are true.
They merely state elements that are not present.

8. Example #3 Major Proposition: No banks hand out free money.
Minor Proposition: Most students do not hand out free money.
Conclusion: Most students are banks.

9. Assumptions
Sometimes it is necessary to add a fourth or even a fifth statement if there are unstated assumptions in the logic of the syllogism.

10. Example #4 Major Proposition: Minor Proposition: Conclusion:
I will starve if I do not receive support.
Minor Proposition:
My parents will not support me.
Conclusion:
I will starve.
Unstated Assumption: My parents are the only possible source of support.