PHILOSOPHY 104

9.2 Notes

SOME DEFINITIONS:

Necessary: When A is a necessary condition for B, that

means that condition A must be fulfilled before condition

B can obtain, but that fulfilling condition A may not be by

itself enough to fulfill condition B.

Sufficient: When A is sufficient for B, that means that all

you need for B to obtain is for condition A to be fulfilled.

However, condition B might still obtain without condition

A being fulfilled.

THE CONDITIONAL

Conditional statements are called conditionals because they

assert necessary and sufficient conditions.

In any given true conditional, the antecedent is a sufficient

condition for the consequent, while the consequent is a necessary

condition for the antecedent.

S N

TESTING NECESSARY AND SUFFICIENT CONDITIONS:

There are two tests for necessary and sufficient

conditions:• The conceptual test: formulate the conditions as a

conditional statement in the appropriate way. True conditionals reveal what is a condition for what, while false conditionals reveal what isn’t a condition for what.

• The empirical test: The SCT and NCT of future slides.

THE NECESSARY CONDITION TEST (NCT)

Some feature F is a necessary condition for having

feature G if and only if anything that lacks feature F

also lacks feature G

Any feature F that is absent when G is present is

eliminated as a possible necessary condition of G.

THE SUFFICIENT CONDITION TEST (SCT)

Some feature F is a sufficient condition for having

feature G if and only if anything that has feature F

also has feature G

So, any feature F that is present when G is absent

is eliminated as a possible sufficient condition of G

THE JOINT TEST

A factor is necessary and sufficient in the case that

it does not fail either NCT or SCT

RIGOROUS TESTING

If you’re looking for candidates for causal factors,

make sure that you have enough examples of each

feature’s presence and absence

This is to rule out coincidence