Great progress has been made by modern science in investigating all the minor details of the shell which man occupies during his life upon this planet; but as regards the inhabitant of that house, the inner man, who is neither wholly material nor wholly spiritual, the ancient sages knew more about his true nature than is ever dreamed of in our medical schools, and it will be undoubtedly worth while to examine their views. Moreover, if the outward body of man is, as they teach, only the outward expression of the qualities and functions of a more interior and invisible human organism; then it appears that many bodily diseases, such as are not caused by direct physical injuries, are the results of disorders existing within that inner organism, and as every true physician should seek to know the causes of diseases, and not merely destroy their external effects, such a knowledge of the “causal body” of man, whose visible image is his “phenomenal form,” may open a new field for pathology and therapeutics, from which a rich harvest may be gathered for the benefit of mankind. I. THE CONSTITUTION OF MAN. From times immemorial the sages have taught that we shall never know immortal truth, if we do not discover it within our own selves. Experience has long ago corroborated this theory, for in spite of all progress in scientific researches concerning the nature of Man, and which were carried on by means of researches in the external kingdom of nature, the real constitution of Man and that which constitutes his essential being has not yet been discovered. We know that from the ovum the fœtus, from the fœtus the child, from the child the body of man becomes developed; we know the order in which these processes take place; but we seem to know nothing about the powers that produce them. Such an alchemical trick of nature as to make a man grow out of a cell in which no man is contained would seem absurd, incredible and miraculous, and would be believed by nobody, if it were not a well-known fact, and being of daily occurrence it has ceased to appear surprising, so that it appears now strange if anyone wonders how such a thing is possible.