There is another class of cases where the adjustments are still more difficult to determine. Innumerable points exist in our surroundings with which it is perfectly legitimate to enjoy, and even to cultivate, correspondence, but which privilege, at the same time, it were better on the whole that we did not use. Circumstances are occasionally such--the demands of others upon us, for example, may be so clamant--that we have voluntarily to reduce the area of legitimate pleasure. Or, instead of it coming from others, the claim may come from a still higher direction. Man's spiritual life consists in the number and fullness of his correspondences with God. In order to develop these he may be constrained to insulate them, to inclose them from the other correspondences, to shut himself in with them. In many ways the limitation of the natural life is the necessary condition of the full enjoyment of the spiritual life. In this principle lies the true philosophy of self-denial. No man is called to a life of self-denial for its own sake. It is in order to a compensation which, though sometimes difficult to see, is always real and always proportionate. No truth, perhaps, in practical religion is more lost sight of. We cherish somehow a lingering rebellion against the doctrine of self-denial--as if our nature, or our circumstances, or our conscience, dealt with us severely in loading us with the daily cross. But is it not plain after all that the life of self-denial is the more abundant life--more abundant just in proportion to the ampler crucifixion of the narrower life? Is it not a clear case of exchange--an exchange however where the advantage is entirely on our side? We give up a correspondence in which there is a little life to enjoy a correspondence in which there is an abundant life. What though we sacrifice a hundred such correspondences? We make but the more room for the great one that is left. The lesson of self-denial, that is to say of Limitation, is _concentration_. Do not spoil your life, it says, at the outset with unworthy and impoverishing correspondences; and if it is growing truly rich and abundant, be very jealous of ever diluting its high eternal quality with anything of earth. To concentrate upon a few great correspondences, to oppose to the death the perpetual petty larceny of our life by trifles--these are the conditions for the highest and happiest life. It is only Limitation which can secure the Illimitable.