“What is the principle of identity in a living body? Assuredly it does not consist in the complete and persistent identity of its _matter_. For in this continual change and renewal, which is the very essence of physiological life, the elements, which have belonged successively from infancy to old age to the same human being, would form a colossal body. In this torrent of life the elements pass and change ceaselessly; but the organism remains the same, notwithstanding the modifications in its size, its form and its constitution. Does the growing stem of the oak, hidden between its two cotyledons, cease to be the same plant when it has become a mighty oak? Is the embryo of the caterpillar, while yet in the egg, no longer the same insect when it becomes a caterpillar, and then a chrysalis, and then a butterfly? Is individuality lost as the child passes through manhood to old age? Assuredly not. But in the case of the oak, the butterfly, and the man, is there a single remaining molecule of those which constituted the growing stem of the oak, the egg of the caterpillar or the human embryo? What then is the principle which persists through all these changes? This principle is a reality, not a fiction. It is not the soul, for the plants have life, and yet no souls, in the meaning of the word as we use it. Nevertheless, it must be an imponderable agent. Does it survive the body? It is possible. St. Gregory of Nyssus believed so. If it remains united to the soul, it may be invoked to furnish it with a new body identical with that which death has destroyed, even though this body should not possess _a single molecule_ which it possessed at any period of its terrestrial life, and this would be as truly our body as that which we had when five, fifteen, or thirty, or sixty years of age. “Such a conception agrees perfectly with the expressions of holy writ, according to which it is certain that after a period of separation the soul will again take on the body forever. “In addition to St. Gregory of Nyssus, permit me, most reverend fathers, to cite a philosopher Leibnitz, who held the opinion that the physiological principle of life was imponderable but not incorporeal, and that the soul remains united to this principle, although separated from the ponderable and visible body. I do not pretend to either accept or reject this hypothesis. I only note that it may serve to explain the dogma of the resurrection, in which every Christian should firmly believe.”