Conditional Argument

If the oil pipeline leaks, then my water will be polluted.

The pipeline is leaking. Therefore, my water will be

polluted.

Conditional Argument

If the oil pipeline leaks, then my water will be polluted.

Antecedent Consequent

Conditional Validity

Affirming the antecedent The pipeline is leaking

Denying the consequent My water is not polluted.

Conditional Argument

If the oil pipeline leaks, then my water will be polluted.

Antecedent Consequent

“Unless” or “Only if”

My water will not be polluted, unless the oil pipeline leaks If the oil pipeline does not leak,

then my water will not be polluted. My water is polluted. Therefore, the pipeline is leaking.

Exercise A1 If our administrators were well-

trained, then our schools would be among the best.

Our schools are not among the best. So our administrators must not be

well-trained. Denying the consequent Valid

Exercise A3

If problems do not arise, then the government will not intervene.

Problems arose. So the government intervened.

Denying the antecedent Invalid

Exercise A5

If you raise your children properly, then they will obey you.

You are raising them properly. So they will obey you.

Affirming the antecedent Valid

Exercise A7

If food supplies are short in the south, residents will flee north.

Food is short in the south. Residents will flee north.

Affirming the antecedent Valid in the form stated above

Argument from Direction

If A then B, if B then C. C is undesirable. Therefore, we should not allow

A. Slippery slope argument Remember truth is different from

validity.

Exercise B1 If we kill the terminally ill, then

we will kill the chronically ill. If will kill the chronically ill, then

we will kill those tired of life. The melancholy should be

protected. Therefore, we should not kill the

terminally ill.

Exercise B3 If we fail to recognize a mother’s

rights, then a contract takes precedence over human rights

If a contract takes precedence, then motherhood will depend on payment.

(This is undesirable). Therefore, we should protect a

mother’s rights in surrogacy.

Exercise B5 Neutrality leads to ambivalence. Ambivalence gives way to confusion. (This is undesirable). Therefore, we can not afford to be

politically neutral.

Exercise B7 If bilingualism in schools, then

ghettoization. If ghettoization, then racial

antagonism. (Racial antagonism is

undesirable). Therefore, bilingualism in

schools should be abandoned.

Categorical Argument

All TV news anchors are articulate speakers.

All articulate speakers can adapt to unexpected events.

All TV news anchors can adapt to unexpected events.

End term (D)

End term (D)

Middle term (U)

End term (U)

Middle term (D) End term (U)

Categorical Validity

The middle term must be distributed exactly once.

Neither end term can be distributed only once.

The number of negative premises must equal the number of negative conclusions.

Universal Affirmative Argument

All TV news anchors are articulate speakers.

All articulate speakers can adapt to unexpected events.

All TV news anchors can adapt to unexpected events.

End term (D)

End term (D)

Middle term (U)

End term (U)

Middle term (D) End term (U)

Valid Universal Argument

All TV news anchors (A) are articulate speakers (B).

All articulate speakers (B) can adapt to unexpected events (C).

All TV news anchors (A) can adapt to unexpected events (C).

A B C

Invalid Universal Argument

A B C

All TV news anchors (A) are articulate speakers (B).

All TV news anchors (A) can adapt to unexpected events (C).

All articulate speakers (B) can adapt to unexpected events (C).

Particular Affirmative Argument

All TV news anchors are articulate speakers.

Some TV news anchors are egotistical airheads.

Some articulate speakers are egotistical airheads.

Middle term (D)

Middle term (U)

End term (U)

End term (U)End term (U)

End term (U)

Valid Particular Argument

All TV news anchors (A) are articulate speakers (B).

Some TV news anchors (A) are egotistical airheads (C).

Some articulate speakers (B) are egotistical airheads (C).

AB C

Invalid Particular Argument

A?B C

All TV news anchors (A) are articulate speakers (B).

Some articulate speakers (B) are egotistical airheads (C).

Some TV news anchors (A) are egotistical airheads (C).

Universal Negative Argument

All TV news anchors are egotistical airheads.

No egotistical airheads can adapt to unexpected events.

No TV news anchors can adapt to unexpected events.

End term (D)

End term (D)

Middle term (U)

End term (D)

Middle term (D) End term (D)

Particular Negative Argument

All TV news anchors are articulate speakers.

Some TV news anchors are not egotistical airheads.

Some articulate speakers are not egotistical airheads.

Middle term (D)

Middle term (U)

End term (U)

End term (D)End term (U)

End term (D)

Exercise C1

All tour guides are polite.

All tour-bus drivers are polite.

All tour-bus drivers are tour guides.

End term (D)

End term (D)

Middle term (U)

End term (U)

End term (D) Middle term (U)

•Invalid universal affirmative

Exercise C3

All company employees are well-trained.

Some well-trained people are not competent.

Some company employees are not competent.

End term (D)

End term (U)

Middle term (U)

End term (D)

Middle term (U) End term (D)

•Invalid particular negative

Exercise C5

All poems by Poe are poems that use iambic pentameter.

No poems in this collection use iambic pentameter.

No poems in this collection are poems by Poe.

End term (D)

End term (D)

Middle term (U)

End term (D)

End term (D) Middle term (D)

•Valid universal negative

Enumeration Arguments

Form: Either A or B or C. Not A, and not B. Therefore, C.

Validity: All plausible alternatives Options eliminated convincingly

Exercise D1

The rapid drop in production of goods may be caused by: Lazy blue-collar workers (A). Government regulations (B). New white-collar workers (C).

Not A or B, then C.

Disjunctive Arguments Form:

Either A or B. Not A. Therefore, B.

Disjunctives are usually invalid. Plausible alternatives exist.

A dilemma is when two options are undesirable.

Exercise E1

The future of this nation will be decided by: Enacting strict immigration laws. Letting illegal immigration decide

the future. Conclusion is implied.

Inductive Arguments Inductive arguments may attain a

level of probability, not validity. Analogies are inductive.

A is similar to B in some important ways.

Thus, A is similar to B in another important way.

Assumption: The presence of some similarities suggests the likelihood of other similarities.