{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

L24_Indirect_and_Disjunctive_Syllogisms

# L24_Indirect_and_Disjunctive_Syllogisms - We have learned...

This preview shows pages 1–5. Sign up to view the full content.

We have learned about two types of syllogisms so far: The direct syllogism [Latin name: modus ponens], of the form pΛ(p 0 q), q and the transitive syllogism, of the form (p 0 q)Λ(q 0 r), (p 0 r). Now we learn about two more syllogisms: The indirect syllogism [Latin name: modus tollens], of the form (p 0 q) Λ ~q, ~p . Finally, the disjunctive syllogism has the form (pVq) Λ ~p , q .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Example: I will go to Chicago or you will get \$100. I do not go to Chicago. Therefore you will get \$100. This is an example of a valid disjunctive syllogism. Example: Every dog is a loyal friend. My pet, Sampson, is not a loyal friend. Therefore Sampson is not a dog. This is an example of a valid indirect syllogism.
Discuss the following syllogism: Lucy wears red or Julie wears green. Julie wears green. Therefore Lucy does not wear red. Analysis: Let p: Lucy wears red q: Julie wears green. The syllogism has the form (pVq) Λ q, p which is an invalid syllogism.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Example: Make a valid conclusion from the information p 0 q and q 0 r and ~s 0 ~r.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}