From the back of the box:
Assumption allows you and your friends to be the experts on every topic imaginable, in a game where there is never an incorrect answer.
Assumption is a fun and intriguing game in which each player must assume to know-it-all in order to win! If you can admit to being a know-it-all, have ever been accused of being a know-it-all, or happen to know a know-it-all... Assumption is definitely a game for you!

Object of the game -
To be the player with the best assumptions as to why things are the way they are... to win!!! Assumption is the game where the players decide the best answers to outrageous questions seldom contemplated! Questions like...

Why don't fortune tellers win the lottery?
Why don't nudist camps have age restrictions?
Why do men like old cars and not old women?
Why do they make catheter tubing so large?