A nice way to dig under obvious truths. I learned the basic technique here from Emily Schnee, from whom I learn so much. I have found that many students experience this as a revelation because it calls on them to question again and again when they are typically called on to give one answer.

Take a simple statement of an identity (I am a teacher), or a problem (I don't have enough time to do work I want to do), or just about any simple sentence (slugs leave a trail)...

Spoken version:
The player says her/his sentence out loud, then one person asks "why?"
The player must give a reason; "because..."
Then another person asks "why?" and the player must give a reason for that statement... and so on, until ten whys have been asked and answered.
At the end, the person repeats the original sentence and the tenth reason.

Written version:
Each person writes her/his sentence at the top of a page and then writes ten questions (why) and answers (because...).
At the end, s/he copies the original sentence and the tenth reason.

Example:

I am a university student. ("Why are you a university student?")
Because I want to learn a lot of things. ("Why do you want to learn a lot of things?")
Because I want to get a good job. ("Why do you want to get a good job?")
Because I want to get some money. ("Why do you want to get some money?")
Because I want to travel a lot of places. ("Why do you want to travel to a lot of places?")
Because I want to communicate with many people. ("Why do you want to communicate with many people?")
Because I like to talk with people. ("Why do you like to talk with people?")
Because I can get many ideas. ("Why can you get many ideas?")
Because everyone has different points of view. ("Why does everyone have different points of view?")
Because everyone has a different sense of values. ("Why does everyone have a different sense of values?")
Because everyone has a different life.

I am a university student because everyone has a different life.

Notes:
It is good to encourage people to treat this as a game -- don't take it seriously, we're just playing. That way, people may loosen up and come up with more interesting content.

Watch for tautology: I am a student. Why? Because I study.

Use this to fish for interesting starting points for discussion, but don't force it. It's just a game, until something meaningful comes up.

Variations:
Try this for something obvious and usually unexamined: we are union members... why? why? why?

Try this to talk about our resources of hope. "I have hope for the future." Why? Why? Why?

Gauntlet of Why: Do it as a group game in which one player in the middle makes a statement then goes from person to person, each time being asked "why?" and each time giving a reason for the previous reason. When the person has been questioned ten times, connect that final reason to the initial statement, as in the activity above.

When you get ten levels, look at list and choose most interesting reason. Then, write that reason on a new sheet of paper, and brainstorm reasons why it is true or important, what it means -- the idea is to expand on something interesting.