After all, to some extent we conceive time as reversible, in the conception of historical time. In history we go back in time at our will, and traverse with the mind's eye the times of the past, and we then find that death and extinction do not exist in history, but the events of history, the lives of those who made history, exist just as much outside of the span of time of their physiological life--that is, are immortal in historical time. They may fade and become more indistinct with the distance in time, just as things in space become more indistinct with the distance in space, but they can be brought back to full clearness and distinction by again approaching the things and events, the former moving through space, the latter moving through the historical time--that is, by looking up and studying the history of the time. THE ENTITY "X" Scientifically, life is a physico-chemical process. Transformations of matter, with which the chemist deals, and transformations of energy, with which the physicist deals, are all that is comprised in the phenomenon of life; and mind, intellect, soul, personality, the ego, are mere functions of the physico-chemical process of life, vanishing when this process ceases, but are not a part of the transformations of matter and of energy. If you thus speak of "mental energy," it scientifically is a misnomer, and mind is not energy in the physical sense. It is true that mental effort, intellectual work, is accompanied by transformations of matter, chemical changes in the brain, and by transformations of energy. But the mental activity is not a part of the energy or of the matter which is transformed, but the balance of energy and of matter closes. In the energy transformations accompanying mental activity, just as much energy of one form appears as energy of some other form is consumed, and the mental activity is no part of the energy. In the transformations of matter accompanying mental activity, just as much matter of one form appears as matter of some other form is consumed, and the mental activity is no part of either--that is, neither energy nor matter has been transformed into mental activity, nor has energy or matter been produced by mental activity. All attempts to account for the mental activity as produced by the expenditure of physical energy, or as producing physical energy--that is, exerting forces and action--have failed and must fail, and so must any attempt to record or observe and measure mental activity by physical methods--that is, methods sensitive to the action of physical forces.