All USC students love football.

Jim is a Kentucky student.

So Jim doesn't love football.

-invalid syllogism

All cats meow.

Simba is a cat.

Simba meows.

-valid syllogism

Lastnight some jocks stayed up all night yelling and making bets at a swimming party when they knew the had finals the next day.

Jocks are irresponsible.

Max is a jock.

Max is irresponsible.

-implied syllogism