introductory logic lessons 23-26

lesson 23

100

A syllogism is valid if ....

the conclusion is necessarily true given that the premises are true

200

Is the conclusion true in a valid syllogism?

no

300

Are the premises true in a valid syllogism?

No

400

If a syllogism has true premises and a false conclusion, is it valid or invalid?

invalid

500

If a syllogism is valid and the premises are true, it is said to be ...

sound

lesson 23-25

100

Is the conclusion true in a sound syllogism?

Yes

200

Is a sound syllogism a valid syllogism?

Yes

300

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.

400

A distributed term is a term that, within a statement, refers to ____ (all/some) members of its category.

all

500

All S are P. ---- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)

distributed, undistributed

lesson 25-26

100

No S are P. ---- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)

distributed, distributed

200

Some S are P ----- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)

undistributed, undistributed

300

Some S are not P ----- S is _____ (distributed/undistributed?) and P is ________ (distributed/undistributed?)

undistributed, distributed

400

Testing Syllogisms by Rules:

Rule #1: In at least one premise, the ____ term must be distributed.

middle

500

When Rule #1 is broken, it is known as the Fallacy of _____

the undistributed middle.

lesson 26

100

Testing Syllogisms by Rules:

Rule 2: If a term is distributed in the conclusion, it must also be _____ (distributed/undistributed) in its premise.

distributed

200

If the major term is distributed in the conclusion, but not in the premise, it is known as the Fallacy of ___

an illicit major

300

If the minor term is distributed in the conclusion, but not in the premise, it is known as the Fallacy of ___

an illicit minor

400

Testing Syllogisms by Rules:

Rule 3: A valid syllogism cannot have two _____ (affirmative/negative?) premises

negative

500

If Rule 3 is broken, we say that it. is the Fallacy of 

Two Negative premises

lesson 26

100

Testing Syllogisms by Rules:

Rule 4: A valid syllogism cannot have a negative premise and an _____ (affirmative/negative?) conclusion.

affirmative

200

If Rule 4 is broken, we say that it is the fallacy of _____

a negative premise and an affirmative conclusion.

300

Testing Syllogisms by Rules:

Rule 5: A valid syllogism cannot have two affirmative premises and a _____ (affirmative/negative?) conclusion.

negative

400

When Rule 5 is broken, the syllogism makes the Fallacy of _____

Two Affirmative Premises and a negative conclusion.

500

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.