One very easy application of this axiom is whenever you're near water or rain and don't want to get wet. You're at the beach, climbing on rocks and you're not sure if a wave will hit you if you climb on the next rock. Is the rock wet? If so it will, if it's dry, you're fine. You're next to a sprinkler system and it's going around and you don't know if you'll get hit if you stand here, is the floor wet? And so on.