This is an activity that can be done once students have been introduced to a Thesis, but it can also be used just to start thinking critically about topics. They’ll get to get up and move around the room a little. Depending on how the conversations go, this might last anywhere from 15 to 30 minutes (or longer).
You'll give them a topic and have them choose a physical position that demonstrates a "yes", "no", or "unsure" to help force them choose a side that they'll argue for. This is informal, but it's a good conversation piece.