The Building Blocks of Logic
SYLLOGISMS
IT’S A LITTLE BIT LIKE MATH…
IF A=B
And C=A
Then B=C
All humans have brains.
Mrs. Miedwig is a human.
Mrs. Miedwig has a brain.
SOUND, VALID, OR INVALID?
Sound= The premises are both unequivocally
true
Valid= At least one of the premises is up for
debate
Invalid= The two premises do not have to lead
to that conclusion
RELATIONSHIP TO TOULMIN
Warrant: All humans have a heart.
Data/ Support: Mrs. Miedwig is human.
Claim: Mrs. Miedwig has a heart.
Let’s talk about ORDER:
Warrant: Good schools contain strong fine arts
programs.
Data/ Support: Crystal Lake South has a strong fine
arts program.
Claim: Crystal Lake South is a good school.
ENTHYMEME
A syllogism as stated in writing, typically with one
premise missing. This usually means there’s more to say
to defend your ideas.
Examples:
Assisted suicide is wrong because killing is wrong.
If killing babies is wrong, then abortion is obviously wrong.
Capital punishment is wrong because it is killing someone.
ANOTHER EXAMPLE
Full syllogism –
All
humans are mortal. (This one is left out of the
enthymeme)
Michael is human.
Therefore, Michael is mortal.
Enthymeme – Michael is mortal because he’s
human.
EXAMPLE IN MLK
“Since I feel that you are men of genuine good
will and that your criticisms are sincerely set
forth, I want to try to answer your statement in
what I hope will be patient and reasonable
terms.”
Syllogism:
Sincere criticism from good people should be answered.
You are good people with sincere criticism.
Your criticism should be answered.
ANOTHER EXAMPLE
“The purpose of our direct-action program is to
create a situation so crisis-packed that it will
inevitably open the door to negotiation.”
Syllogism:
Situations that are crisis packed open the door to
negotiation.
The situation we are creating is crisis packed.
Our situation will open the door to negotiation
PRACTICAL APPLICATION
Look for assumptions in your own writing and
be sure to defend them. (Warrants!)
Look for assumptions in other people’s writing
and attack them. (Debates!)
Watch out for invalid syllogisms/ invalid logic.
Example:
Men are stronger than women, so women
cannot serve in the military.
“THE CASE FOR TORTURE”
Find examples where Levin uses syllogisms
within his argument and write them out.
Write a syllogism for Levin’s OVERALL
argument.
Is Levin’s argument sound? valid? invalid?
Explain your answer.
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