Obverse Relationships
What is obversion?
Changing the quality of the subject and predicate
What is conversion?
Switching the subject and predicate
What is Contraposition?
Doing obversion, then conversion, then obversion again
What is Immediate Inference?
Changing one thing into another equivalent thing
How do you create a complement (in logic)
Put a 'non' at the beginning of a term
The only propositions that can be obverted
What is A, E, I and O propositions?
The only propositions that can be used in converse relationships
What is E and I propositions?
The only propositions that can be used with Contraposition
What is A and O propositions?
Identify the immediate inference and tell whether it is a valid one.
No snackles are boojiminys, therefore no boojiminys are snackles.
Conversion
Yes, conversion on an E proposition is valid.
How is a complement different from an antonym?
Antonym is the opposite; complements include anything outside the term.
State obverse sentence:
"No thing that is worth learning can be taught.” — Oscar Wilde
All thing that is worth learning is non-that can be taught.
State converse sentence:
No people are non-sinners.
No non-sinners are people.
Contrapose the sentence:
All dogs are fierce creatures.
All non-fierce creatures are non-dogs.
Identify the immediate inference and tell whether it is a valid one.
Some non-snarks are boojums, therefore, some non-snarks are not non-boojums.
Obversion
Yes, obversion on an I propositiotion is valid
Contrapose:
Some S are not PSome non-P are not non-S.
Translate into categorical form and write an equivalent proposition (obverse):
None failed the test.
No students are that which failed the test.
Answer: All students are non-that which failed the test.
Translate into categorical form and write an equivalent proposition (converse):
Many people have hair.
Some people is that which have hair.
Answer: Some things that have hair are people.
Translate into categorical form and Contrapose it:
People like food.
All people like food.
Answer: All non-food likers are non-people.
Identify the immediate inference and tell whether it is a valid one.
All boojums are non-snarks, therefore, all non-snarks are boojums.
Conversion
No, conversion on an A proposition is NOT valid.
What is required for a sentence to be in categorical form?
Quantifier, subject, copula, and predicate (in that order).
Translate into categorical form and write an equivalent proposition (obverse):
A few days of the week are not busy.
Some days of the week are not busy days.
Answer: Some days of the week are non-busy days.
Translate into categorical form and write an equivalent proposition (converse):
One student made an A.
Some students are that which made A's.
Answer: Some of that which made A's are students.
Translate into categorical form and contrapose it:
Many snarks are not lovers of boojims.
Some snarks are not that which is lovers of boojims.
Answer: Some non-that which is lovers of boojims are not non-snarks.
Identify the immediate inference and tell whether it is a valid one.
Some non-snarks are not non-boojims, therefore some boojims are not snarks.
Contraposition
Yes, contraposition on an O proposition is valid.
Why are relationships of equivalence helpful?
They help us to see things in a different way and can clarify confusing propositions (with multiple negatives).