In climbing a mountain, if we know the path and take it as a matter of course, we are free to enjoy the beauties of the surrounding country. If in the same journey we set a stone in the way and recognize our ability to step over it, we do so at once, and save ourselves from tripping or from useless waste of time and thought as to how we might best go round it. There are stones upon stones in every-day life which might be stepped over with perfect ease, but which, curiously enough, are considered from all sides and then tripped upon; and the result is a stubbing of the moral toes, and a consequent irritation of the nervous system.