That condition is that the Environment be perfect. If it is not perfect, if it is not the highest, if it is endowed with the finite quality of change, there can be no guarantee that the Life of its correspondents will be eternal. Some change might occur in it which the correspondents had no adaptive changes to meet, and Life would cease. But grant a spiritual organism in perfect correspondence with a perfect spiritual Environment, and the conditions necessary to Eternal Life are satisfied. The exact terms of Mr. Herbert Spencer's definition of Eternal Life may now be given. And it will be seen that they include essentially the conditions here laid down. "Perfect correspondence would be perfect life. Were there no changes in the environment but such as the organism had adapted changes to meet, and were it never to fail in the efficiency with which it met them, there would be eternal existence and eternal knowledge." [1] Reserving the question as to the possible fulfilment of these conditions, let us turn for a moment to the definition of Eternal Life laid down by Christ. Let us place it alongside the definition of Science, and mark the points of contact. Uninterrupted correspondence with a perfect Environment is Eternal Life according to Science. "This is Life Eternal," said Christ, "that they may know Thee, the only true God, and Jesus Christ whom Thou has sent." [2] Life Eternal is to know God. To know God is to "correspond" with God. To correspond with God is to correspond with a Perfect Environment. And the organism which attains to this, in the nature of things must live for ever. Here is "eternal existence and eternal knowledge." [1] "Principles of Biology," p. 88. [2] John xvii.