The second test is at least not so manifestly impracticable. It is to apply the ordinary methods by which biology attempts to distinguish the organic from the inorganic. The characteristics of Life, according to Physiology, are four in number--Assimilation, Waste, Reproduction, and Spontaneous Action. If an organism is found to exercise these functions, it is said to be alive. Now these tests, in a spiritual sense, might fairly be applied to the spiritual man. The experiment would be a delicate one. It might not be open to every one to attempt it. This is a scientific question; and the experiment would have to be conducted under proper conditions and by competent persons. But even on the first statement it will be plain to all who are familiar with spiritual diagnosis that the experiment could be made, and especially on one's self, with some hope of success. Biological considerations, however, would warn us not to expect too much. Whatever be the inadequacy of Morphology, Physiology can never be studied apart from it; and the investigation of function merely as function is a task of extreme difficulty. Mr. Herbert Spencer affirms, "We have next to no power of tracing up the genesis of a function considered purely as a function--no opportunity of observing the progressively-increasing quantities of a given action that have arisen in any order of organisms. In nearly all cases we are able only to establish the greater growth of the part which we have found performs the action, and to infer that greater action of the part has accompanied greater growth of it."[97] Such being the case, it would serve no purpose to indicate the details of a barely possible experiment. We are merely showing, at the moment, that the question "How do I know that I am alive" is not, in the spiritual sphere, incapable of solution. One might, nevertheless, single out some distinctively spiritual function and ask himself if he consciously discharged it. The discharging of that function is, upon biological principles, equivalent to being alive, and therefore the subject of the experiment could certainly come to some conclusion as to his place on a biological scale. The real significance of his actions on the moral scale might be less easy to determine, but he could at least tell where he stood as tested by the standard of life--he would know whether he were living or dead. After all, the best test for Life is just _living_. And living consists, as we have formerly seen, in corresponding with Environment. Those therefore who find within themselves, and regularly exercise, the faculties for corresponding with the Divine Environment, may be said to live the Spiritual Life.