=Gross Dependence.= The relation of mind to body has always been an interesting one to man. This is partly because of the connection of the question with that of life after death. An old idea of this relation, almost universally held till recently, was that the mind or spirit lived in the body but was more or less independent of the body. The body has been looked upon as a hindrance to the mind or spirit. Science knows nothing about the existence of spirits apart from bodies. The belief that after death the mind lives on is a matter of faith and not of science. Whether one believes in an existence of the mind after death of the body, depends on one's religious faith. There is no scientific evidence one way or the other. The only mind that science knows anything about is bound up very closely with body. This is not saying that there is no existence of spirit apart from body, but that at present such existence is beyond the realm of science. The dependence of mind upon body in a general way is evident to every one, upon the most general observation and thought. We know the effect on the mind of disease, of good health, of hunger, of fatigue, of overwork, of severe bodily injury, of blindness or deafness. We have, perhaps, seen some one struck upon the head by a club, or run over by an automobile, and have noted the tremendous consequences to the person's mind. In such cases it sometimes happens that, as far as we can see, there is no longer any mind in connection with that body. The most casual observation, then, shows that mind and body are in some way most intimately related. =Finer Dependence.= Let us note this relation more in detail, and, in particular, see just which part of the body it is that is connected with the mind. First of all, we note the dependence of mind upon sense organs. We see only with our eyes. If we close the eyelids, we cannot see. If we are born blind, or if injury or disease destroys the retinas of the eyes or makes the eyes opaque so that light cannot pass through to the retinas, then we cannot see. Similarly, we hear only by means of the ears. If we are born deaf, or if injury destroys some important part of the hearing mechanism, then we cannot hear. In like manner, we taste only by means of the taste organs in the mouth, and smell only with the organs of smell in the nose. In a word, our primary knowledge of the world comes only through the sense organs. We shall see presently just how this sensing or perceiving is accomplished.