Necessary conditions are like minimun requirements.
A
is a necessary condition of B if and only if B cannot occur without the
occurrence of A.
Or
A
is
a necessary condition of B if B
could not be the case without A being
the case.
Example: Oxygen is a necessary condition for fire, but not
sufficient.
In
other words
This (Oxygen) is a necessary condition for that (fire) if and
only if that (fire) cannot be without this (Oxygen).
A necessary condition for the occurrence of a specified event (fire) is
a circumstance (Oxygen) in whose absence the event cannot
occur.
Sufficient conditions, instead,
are enough to bring about a particular event or property.
A
is a sufficient condition of B if and only if whenever A occurs, B also occurs.
Or
A
is
a sufficient condition of B if A
could not be the case without B's being
the case.
Example: Sugar
is a
SUFFICIENT condition for sweetness.
In
other words
This (Sugar) is a sufficient condition for that (sweetness)
if
and only if this (Sugar)
alone
guarantees that (sweetness).
A
sufficient condition for the occurrence of a specified event (sweetness) is
a circumstance in whose presence (Sugar) the event (sweetness)
will occur.
Exercises
Directions: Label the relationship between the given examples as
either:
(1)
Necessary (but NOT sufficient),
(2)
Sufficient (but NOT necessary),
(3)
Neither necessary nor sufficient.
1. Fire is a ______________ condition for
oxygen.
2. Striking a match is a ______________
condition for lighting a match.
3. Sweetness is a _______________ condition for
sugar.
4. Five nickels is a ___________ condition for
twenty-five cents.
5. Blackness is a _____________ condition for
being a raven.
6. Being at least 15 years of age is a
_____________ condition for being 25 years of age.
7. Mortality is a _____________ condition for
being a human.
8. Yellowness is a ________________ condition
for being a banana.
9. A banana is a _____________ condition for
yellowness.
10. Being a flower is a _______________
condition for being a rose.
11. Being a bachelor is a _______________ condition
for an unmarried adult male.
ANSWERS
1. Fire is a ______________ condition for
oxygen. SUFFICIENT
2. Striking a match is a ______________
condition for lighting a match. NEITHER NECESSARY NOR SUFFICIENT (it might
not light, or you could light the match with a lighter)
3. Sweetness is a _______________ condition for
sugar. NECESSARY (if it is granulated, not cane sugar)
4. 5 nickels is a ___________ condition for
twenty-five cents. SUFFICIENT
5. Blackness is a _____________ condition for
being a raven. NECESSARY
6. Being at least 15 years of age is a
_____________ condition for being 25 years of age. NECESSARY
7. Mortality is a _____________ condition for
being a human. NECESSARY (all humans are mortal)
8. Yellowness is a ________________ condition
for being a banana. NEITHER NECESSARY OR SUFFICIENT (the banana might be
black)
9. A banana is a _____________ condition for
yellowness. NEITHER NECESSARY OR SUFFICIENT (the banana might be black)
10. Being a flower is a _______________
condition for being a rose. NECESSARY
11. Being a bachelor is a _______________ condition
for an unmarried adult male. BOTH (??)