The Language of Argument

2 2 2

C H A P T E R 1 0 ■ C a u s a l R e a s o n i n g

opposite target feature, ~G. It also might be necessary for features A, B,

and D. Nothing in Cases 1–4 rules out these possibilities. Thus, even after

Case 4, we cannot say simply that C is not a necessary condition. Case 4

shows that candidate feature C is not a necessary condition for target feature

G, but C still might be necessary for something else. The same point applies to

sufficient conditions as well. In Table 1, Case 2 ruled out the possibility that

candidate feature B is sufficient for target feature G, but none of the cases in

Table 1 show that B is not sufficient for target feature C. To avoid confusion,

then, it is always important to specify the target feature when talking about

what is or is not a necessary or sufficient condition.

The Joint Test

It is also possible to apply these rules simultaneously in the search for possi-

ble conditions that are both sufficient and necessary. Any candidate cannot be

both sufficient and necessary if it fails either the SCT or the NCT. In Table 2,

C is the only possible necessary condition for G, and it is not also a possible

sufficient condition for G, since C fails the SCT in Case 1, where C is present

and G is absent. In Table 1, however, D is a possible sufficient condition of G,

because D is never present when G is absent; and D might also be a neces-

sary condition for G, since G is never present when D is absent. Thus, none of

Cases 1–3 in Table 1 eliminates D as a candidate for a condition that is both

sufficient and necessary for G. As before, this possibility still might be refuted

by Case 4, so any inference to a positive conclusion that some candidate is a

necessary and sufficient condition must be defeasible and, hence, inductive.

For each of the following tables determine

a. Which, if any, of the candidates—A, B, C, or D—is not eliminated by the

sufficient condition test as a sufficient condition for target feature G?

b. Which, if any, of the candidates—A, B, C, or D—is not eliminated by the

necessary condition test as a necessary condition for target feature G?

c. Which, if any, of the candidates—A, B, C, or D—is not eliminated by either

test?

Example: Case 1: A B ~C D ~G

Case 2: ~A B C D G

Case 3: A ~B C D G

a. Only C passes the SCT.

b. Only C and D pass the NCT.

c. Only C passes both tests.

Exercise III

97364_ch10_ptg01_215-238.indd 222 15/11/13 10:48 AM

some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materiallyCopyright 201^3 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights,

affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.