Push it

Chad used to tell the following story (hopefully he’ll forgive me for butchering it here): he was sitting in a restaurant with a colleague. On the table were various dishes and glassware. In the middle of a conversation, the colleague interrupted with a two-word command: “Push it.”

“What?” asked Chad. “Just push it,” the colleague repeated, this time throwing a sideways glance towards a water glass near the edge of the table. “Push it.” So he did. The glass fell, shattered, made a racket and a mess.

Why did he do it? More importantly, what made her think if it? What is it in any of us that makes us look at something - or someone - on the edge and instead of thinking “I’d better move that/him/her back,” we think, “all it would take is one small push...”