Physicians are agreed that there is no entirely satisfactory definition for health. We all know quite well what we mean when we use the word, but it does not admit of such exact limitations as would make a scientific formulation of its meaning. Religion is another of the words which, in spite of its common use, is extremely difficult to define exactly, and it has often been said that we have no definition that will satisfy all those who profess religion and certainly not all those who have made a study of it from the standpoint of the science of theology. As is true of health, each of us knows pretty thoroughly what we mean when we use the word, though our definitely formulated signification for it might not meet with the approval of others, especially of those who are exacting in their requirements. With the two principal words in the title incapable of exact definition, it might seem that the subject matter of this book would be rather vague at best and unpromising in practical significance. But all this indefiniteness is in theory. There are no two words in the language that are more used than health and religion, none that are less vague in practice and no two subjects have a wider appeal or a more paramount interest. The linking them together for discussion in common because of their mutual influence will serve to {2} throw light on both of them and undoubtedly help toward a better understanding of each. Ordinarily the most satisfactory definition of a word can be obtained from its etymology. Unfortunately in the matter of religion there is a very old-time division of opinion as to the derivation of the word which makes etymology of less definite significance than usual. Cicero suggested that _religio_ came from _relegere_, to go through or over again in reading, speech or thought, as prayers and religious observances generally are repeated. On the other hand St. Augustine and Lactantius insisted on deriving _religio_ from the Latin verb _religare_, which means to bind again, to bind back, to bind fast. The word obligation has an analogous origin and illustrates the meaning of religion as if its form from etymology should have been religation. It is this latter derivation that has been most commonly accepted in the modern time. A man may recognize the existence of God and yet not feel any particular obligations toward Him, but if he binds himself anew to the deity whom he recognizes, by trying to make his life accord with the divine will as he views it, then he practices religion. James Martineau said, "By religion I understand the belief and worship of Supreme Mind and Will, directing the universe and holding moral relations with human life." What will occupy us in this book is the effect of this profound feeling and sense of obligation toward a higher power on health, that is, on that wholeness of body and mind which constitutes a normal condition for human beings.