We find ourselves living an apparently dual life, with its bodily and psychical sides. As to both, we have a certain constitution, the nature and laws of which we may not wisely ignore anywhere. We can regard the constitution of our being and its laws, if we will, as hindrances to be fought against; and the religious life seems often so to have viewed the matter. But it ought not to require much thinking to see that such a course is not only suicidal, but particularly for a thorough-going theistic view, is utterly self-contradictory; for the theistic view must recognize in the nature of men an expression of the will of God himself. The religious life, peculiarly, therefore, is driven to see in the laws of man's being—what scientific discovery and invention see in the laws of nature—not limitations, but the possibility of constantly extending power. Let us make it unmistakably clear to ourselves, then, that it is not beneath the dignity of the spiritual life thoroughly to learn the lesson of modern science: that no conditions are trivial, and that none may be safely ignored.
This certainly means, in the first place, that for the present world, at least, the spiritual life has its bodily conditions. It cannot blindly ignore them, without itself inviting into its heart the sense of unreality. This is to be said neither boastingly nor cynically. It is to be faced as a simple fact. We have bodies, and we cannot set ourselves free from them. As I have elsewhere said.
The long sad history of asceticism in all lands shows how real the religious life has felt this connection with the body to be, and at the same time how fiercely it has resented it. Men have remained, in this question of asceticism, quite too largely on the mythological plane, without any clear sense of a real nature and unity of things. The scientific spirit, which demands a careful study of detailed connections and conditions, has had little enough to do with this blind, fierce struggle; and, in consequence, the ascetic has everywhere, on the one hand, failed to take any sensible account of the effects of ordinary bodily conditions; and, on the other hand, paradoxically enough, has exalted the effects of certain abnormal bodily conditions into higher spiritual attainments. These historical results of religious asceticism certainly cannot be held to commend the method of ignoring bodily conditions. The plain lesson of modern science here would seem to be, that, if the spirit is ever to master the body, it must know its laws and take account of its conditions; these are the very instruments of its mastery. So, and only so, has science made nature serve it.
One can quite understand the reluctance, of the spiritual life to admit the closeness of its connection with the physical. It seems itself to be lowered thereby. But it gets no freedom and power by vehemently denying the fact, and ignoring the resulting conditions. Rather, its superiority must be shown, its freedom and power declared, as has been implied, by patient study of the laws of this body and of its connection with the spirit, and by steady fulfilment of the conditions by which alone mastery can come. It is a false and abstract spiritualism, therefore, that hesitates clearly to recognize or to affirm the bodily conditions of the spiritual life. Let us frankly admit that much of the dissatisfaction of the moral and spiritual life results from a wholly unnecessary and senseless disregard of bodily conditions. The emphasis of modern psychology upon the close connection of body and mind, thus, compels the thoughtful man to a study of the bodily conditions of true living.
The man, thus, who means to be saved from misconception of the spiritual life through ignoring its bodily conditions must bear in mind, for example, the need of well oxygenated blood, and the special need of surplus nervous energy as a chief physical condition of self-control. He will not forget here, then, the inevitable effect of fatigue on attention, and consequently upon self-control. Nor will he forget the close connection of muscular activity and will, nor the physical basis of habit. And, on the other hand, he will recognize the influence of the mind over the body, and especially the power of the will in determining conditions of health, in achieving rest, in avoiding hurry, and in meeting the special conditions of surplus nervous energy. He will remember, as well, the physiological effects of faith, and the possible great liberating force of religion in setting free the powers of man.
 Rational Living, pp. 47-49.