Exam 2

Subjectivism

using the fact that one belives or wants a proposition to be true as evidence of its truth:

I believe/want p to be true

p

Appeal to the majority

using the fact that large numbers of people believe a proposition to be true as evidence of its truth:

the majority of people believe that p

p

Appeal to emotion

trying to get someone to accept a proposition on the basis of an emotion one elicits:

no specific form

Appeal to force

trying to get someone to accept a proposition on the basis of a threat:

no specific form

Ad hominem

using a negative trait of the speaker as evidence that his statement is false or his argument weak:

X says p or stands for p + X has some negative trait

p is false or we should reject p

Appeal to authority

using testimonial evidence for a proposition when the conditions for credibility are not satisfied or the use of such evidence is inappropriate:

X says p

p

False dichotomy

excluding relevant possiblities without justification:

either p or q + not q

p

Post hoc (ergo propter hoc)

using the fact that one event preceded another as sufficient evidence for the conclusion that the first caused the second:

A occurred before B

A caused B

Hasty generalization

inferring a general proposition from an inadequate sample of particular cases:

no specific form

Accident

applying a generalization to a special case in disregard of qualities or circumstances that make it an exception to the generalization:

no specific form

Slippery slope

arguing that a proposed action or policy by claiming, without sufficient evidence, that it will lead to a series of increasingly bad consequences:

(action A → consequence B) + (B → C) + (C → D) + D would be very bad

we should not do A

Composition

inferring that a whole has a property merely because its parts have that property:

all the parts of A have properties P1-Pn

A has properties P1-Pn

Division

inferring that a part has a property merely because the whole has that property:

A has properties P1-Pn and B is a part of A

B has properties P1-Pn

Begging the question (Circular argument)

trying to support a proposition with an argument in which that proposition is a premise/assumption:

p

p

Equivocation

using a word in two different meanings in the premises and/or conclusion:

no specific form

Appeal to ignorance

using the absence of a proof for a proposition as evidence for the truth of the opposing proposition:

p has not been proven false

p is true

or…

p has not been proven true

p is false

Diversion (Red herring)

trying to support one proposition by arguing for another proposition:

q, r, s, etc, support t

p

Straw man

the distorting, weakening, or oversimplifying of someone’s position so it can be more easily attacked or refuted:

if p, then q

p = q

Validity

a valid argument is one in which it is not possible for the premises to be true and the conclusion false

Categorical logic

the branch of dedutive reasoning that deals with categorical propositions (propositions that make assertions about categories or classes of things)

Subject term

the subject of the categorical proposition

ex: all cows are herbivores

Predicate term

the predicate (object) of the categorical proposition

ex: all cows are herbivores

Copula

the linking verb between the subject and predicate terms

ex: all cows are herbivores

Quantifier

the word that expresses the quantity or number of a categorical proposition (all, no, or some)

all and no are universal quantifiers

some is a particular quantifier

ex: all cows are herbivores

Quality

refers to whether the categorical statement is affirmative or negative

ex: ‘no cows can fly’ is a negative categorical statement

ex: ‘some cows can fly’ is an affirmative categorical statement

What are the standard form and quality of ‘A’?

Standard form: All S are P

Quality: Universal affirmative

What are the standard form and quality of ‘E’?

Standard form: No S are P

Quality: Universal negative

What are the standard form and quality of ‘I’?

Standard form: Some S are P

Quality: Particular affirmative

What are the standard form and quality of ‘O’?

Standard form: Some S are not P

Quality: Particular negative

Contraries

cannot both be true but could both be false

Subcontraries

cannot both be false but could both be true

Contradictories

have opposite truth values

Subalternates

the truth of the universal implies the truh of the particular, but the truth of the particular leaves the truth of the universal undetermined

Conversion

switching the subject and predicate terms

ex: some englishmen are scotch drinkers → some scotch drinkers are englishmen

Obversion

(1) changing the quality of the statement and (2) changing the predicate term to its class complement

ex: some englishmen are scotch drinkers → some englishmen are not non-scotch drinkers

ex: no sightings of UFOs are things that have been confirmed → all sightings of UFOs are things that have not been confirmed

Contraposition

(1) switching the subject and predicate terms and (2) changing the subject and predicate terms to its class component

it is only valid to infer the contrapositive of A and O categorical statements

ex: some englishmen are scotch drinkers → some non-Scotch drinkers are non-Englishmen

ex: all whales are mammals → all non-mammals are non-whales

Rules of validity (4)

1. Undistributed middle: the middle term must be distributed in at least one of the premises.

2. Illicit major or minor terms: if either of the terms in the conclusion is distributed, it must be distributed in the premise in which it occurs

3. Double negative: the premises cannot both be negative

4. Negative premise/conclusion: if the premise is negative, then the conclusion must be negative; if the conclusion is negative, then a premise must be negative

Enthymeme

an argument in which one premise is not explicitly stated