lesson 23
A syllogism is valid if ....
the conclusion is necessarily true given that the premises are true
Is the conclusion true in a sound syllogism?
Yes
No S are P. ---- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)
distributed, distributed
Testing Syllogisms by Rules:
Rule 2: If a term is distributed in the conclusion, it must also be _____ (distributed/undistributed) in its premise.
distributed
Testing Syllogisms by Rules:
Rule 4: A valid syllogism cannot have a negative premise and an _____ (affirmative/negative?) conclusion.
affirmative
Is the conclusion true in a valid syllogism?
no
Is a sound syllogism a valid syllogism?
Yes
Some S are P ----- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)
undistributed, undistributed
If the major term is distributed in the conclusion, but not in the premise, it is known as the Fallacy of ___
an illicit major
If Rule 4 is broken, we say that it is the fallacy of _____
a negative premise and an affirmative conclusion.
Are the premises true in a valid syllogism?
No
A counterexample to a syllogism is a syllogism of the same form as the original, but with obviously _____ (true/false?) premises and an obviously _____ (true/false?) conclusion, in order to show the original to be invalid.
true, false.
Some S are not P ----- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)
undistributed, distributed
If the minor term is distributed in the conclusion, but not in the premise, it is known as the Fallacy of ___
an illicit minor
Testing Syllogisms by Rules:
Rule 5: A valid syllogism cannot have two affirmative premises and a _____ (affirmative/negative?) conclusion.
negative
If a syllogism has true premises and a false conclusion, is it valid or invalid?
invalid
A distributed term is a term that, within a statement, refers to ____ (all/some) members of its category.
all
Testing Syllogisms by Rules:
Rule #1: In at least one premise, the ____ term must be distributed.
middle
Testing Syllogisms by Rules:
Rule 3: A valid syllogism cannot have two _____ (affirmative/negative?) premises
negative
When Rule 5 is broken, the syllogism makes the Fallacy of _____
Two Affirmative Premises and a negative conclusion.
If a syllogism is valid and the premises are true, it is said to be ...
sound
All S are P. ---- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)
distributed, undistributed
When Rule #1 is broken, it is known as the Fallacy of _____
the undistributed middle.
If Rule 3 is broken, we say that it. is the Fallacy of
Two Negative premises
All whales are sea creatures.
Some sea creatures are warm-blooded animals.
Therfore, no warm-blooded animals are whales.
Which fallacy does it make?
Fallacy of Two affirmative premises and a negative conclusion.