WEEK 4 - Necessary and Sufficient Conditions and Possibility and Necessity Flashcards
what is necessary condition ?
X is a necessary condition for Y just in case
X is required for Y
what do necessary and sufficient conditions do ?
provide us with a clear way of thinking about such relations
what is a sufficient condition ?
X is a sufficient condition for Y just in case
X guarantees Y
(equivalent)
X is a sufficient condition for Y just in case it is impossible for X to obtain but not
what is the relation between necessary and sufficient conditions ?
X is a necessary condition for Y just in case it is impossible for Y to obtain without X obtaining
X is a sufficient condition for Y just in case it is impossible from X to obtain without Y obtaining.
any two conditions X and Y are related in one of four ways :
- X is both necessary and sufficient for Y.
- X is necessary but not sufficient for Y.
- X is sufficient but not necessary for Y.
- X is neither necessary nor sufficient for Y.
what are the the four kids of possibility ?
- logical impossibility
- nomological impossibility
- legal impossibility
- moral possibility
what does it mean to be logically impossible ?
a state of affairs is logically possible just in case it is not contradictory
the following are examples of what type of possibilities :
- It is logically impossible for a triangle to have four sides
- It is logically impossible for 2 to be odd
- Turning Water into gold is logically possible
- It is logically possible for the world to end now
logically possible
what is nomological possibility ?
possibility under the actual laws of nature
what is nomological possibility ?
possibility under the actual laws of nature
what is legally possible ?
Something is legally possible just in case it is permitted by the legal laws
what is morally possible ?
Something is morally possible just in case it doesn’t contradict the rules of morality
