Without uncertainty and exposure there would be no risk. I like the parachute analogy: In jumping out of an airplane with a parachute, there may be uncertainty as to whether the parachute will actually open. The jumper is taking a risk by being exposed to that uncertainty. Jumping out of an airplane without a parachute entails no risk as death is certain. Of course, the decidedly risk-averse shouldn't conclude to leave airplanes in mid-flight without a parachute. It wouldn't be risky but it would be foolish.