Unit 3.5 Flashcards
What is a counterexample?
A counterexample is a syllogism of the same form as the original but with obviously true premises and an obviously false conclusion in order to show the original invalid.
The validity of syllogisms depends on what?
It depends solely on their form. Certain forms are always valid; other forms are always invalid.
What is a distributed term?
A distributed term is a term that, within a statement, refers to all members of its category.
Which term is distributed in All S is P?
S
Which term is distributed in No S is P?
S and P
Which term is distributed in Some S is P?
Neither
Which term is distributed in Some S is not P?
P
Does the square of opposition relate to the distribution of statements?
Yes. The contradicting statements have an opposite distribution of terms.
What is Rule 1 of testing syllogisms by rules?
In at least one premise, the middle term must be distributed. Not doing this is called the Fallacy of the Undistributed Middle.
What is Rule 2 of testing syllogisms by rules?
If a term is distributed in the conclusion, it must also be distributed in its premise. Not doing this is called either Illicit Major or Illicit Minor.
What is Rule 3 of testing syllogisms by rules?
A valid syllogism cannot have two negative premises. Not doing this is called Fallacy of Two Negative Premises.
What is Rule 4 of testing syllogisms by rules?
A valid syllogism cannot have two affirmative premises and a negative conclusion. Basically, the conclusion type has to match at least one premise. Not doing this is called Fallacy of Two Affirmative Premises and a Negative Conclusion.
