Sufficient vs. Necessary - LSAT Prep

Preston and John will go only if Zane drives.

This is a necessary factor. If Zane doesn't drive, Preston and John won't go.

Jack won't eat dinner unless Elba eats with him.

This is a necessary factor. The necessary condition is that Elba eat with him. If Elba doesn't eat with him, Jack won't eat dinner.

We will go to the zoo unless it rains.

This is a necessary factor. The necessary condition is that it not rain. If it doesn't rain, we will definitely go to the zoo.

Carolyn will wear a coat only if the temperature is below freezing.

This is a necessary factor. Unless the temperature is below freezing, Carolyn won't wear a coat.

Only if Walter's jacket and tie are both clean will he attend the ceremony.

This is a necessary factor. Walter won't go without a clean jacket and tie.

I will go to the party only if there is cake.

This is a necessary factor. Without the cake, the result is not achieved.

If Bob milks the cows, Erlene will till the garden.

This is a sufficient factor. If Bob milks the cows, that is sufficient for Erlene to till the garden.

Preston and John will go iI Zane drives.

This is a sufficient factor. If Zane drives, Preston and John definitely will go, but there might be other conditions under which they would go.

My car won't start iI the battery is dead.

This is a sufficient factor. If the battery is dead, the car definitely won't start, but the car might not start for other reasons.

I will buy a new car today iI the model I want is on sale at the dealership near my house.

This is a sufficient factor. If the car is on sale, the result is definitely achieved, but it might also be achieved for other reasons.

Necessary factors

Those that are necessary to produce a particular result. They may not be sufficient alone to produce the result, but they are necessary. A necessary factor may be considered a minimum requirement.

Sufficient factors

Those that are sufficient alone to produce a particular result.