Before giving, in so many words, the definition of Mr. Herbert Spencer, it will render it fully intelligible if we gradually lead up to it by a brief rehearsal of the few and simple biological facts on which it is based. In considering the subject of Death, we have formerly seen that there are degrees of Life. By this is meant that some lives have more and fuller correspondence with Environment than others. The amount of correspondence, again, is determined by the greater or less complexity of the organism. Thus a simple organism like the Amoeba is possessed of very few correspondences. It is a mere sac of transparent structureless jelly for which organization has done almost nothing, and hence it can only communicate with the smallest possible area of Environment. An insect, in virtue of its more complex structure, corresponds with a wider area. Nature has endowed it with special faculties for reaching out to the Environment on many sides; it has more life than the Amoeba. In other words, it is a higher animal. Man again, whose body is still further differentiated, or broken up into different correspondences, finds himself en rapport with his surroundings to a further extent. And therefore he is higher still, more living still. And this law, that the degree of Life varies with the degree of correspondence, holds to the minutest detail throughout the entire range of living things. Life becomes fuller and fuller, richer and richer, more and more sensitive and responsive to an ever-widening Environment as we rise in the chain of being.

Now it will speedily appear that a distinct relation exists, and must exist, between complexity and longevity. Death being brought about by the failure of an organism to adjust itself to some change in the Environment, it follows that those organisms which are able to adjust themselves most readily and successfully will live the longest. They will continue time after time to effect the appropriate adjustment, and their power of doing so will be exactly proportionate to their complexity—that is, to the amount of Environment they can control with their correspondences. There are, for example, in the Environment of every animal certain things which are directly or indirectly dangerous to Life. If its equipment of correspondences is not complete enough to enable it to avoid these dangers in all possible circumstances, it must sooner or later succumb. The organism then with the most perfect set of correspondences, that is, the highest and most complex organism, has an obvious advantage over less complex forms. It can adjust itself more perfectly and frequently. But this is just the biological way of saying that it can live the longest. And hence the relation between complexity and longevity may be expressed thus—the most complex organisms are the longest lived.

To state and illustrate the proposition conversely may make the point still further clear. The less highly organized an animal is, the less will be its chance of remaining in lengthened correspondence with its Environment. At some time or other in its career circumstances are sure to occur to which the comparatively immobile organism finds itself structurally unable to respond. Thus a Medusa tossed ashore by a wave, finds itself so out of correspondence with its new surroundings that its life must pay the forfeit. Had it been able by internal change to adapt itself to external change—to correspond sufficiently with the new environment, as for example to crawl, as an eel would have done, back into that environment with which it had completer correspondence—its life might have been spared. But had this happened it would continue to live henceforth only so long as it could continue in correspondence with all the circumstances in which it might find itself. Even if, however, it became complex enough to resist the ordinary and direct dangers of its environment, it might still be out of correspondence with others. A naturalist for instance, might take advantage of its want of correspondence with particular sights and sounds to capture it for his cabinet, or the sudden dropping of a yacht's anchor or the turn of a screw might cause its untimely death.

Again, in the case of a bird in virtue of its more complex organization, there is command over a much larger area of environment. It can take precautions such as the Medusa could not; it has increased facilities for securing food; its adjustments all round are more complex; and therefore it ought to be able to maintain its Life for a longer period. There is still a large area, however, over which it has no control. Its power of internal change is not complete enough to afford it perfect correspondence with all external changes, and its tenure of Life is to that extent insecure. Its correspondence, moreover, is limited even with regard to those external conditions with which it has been partially established. Thus a bird in ordinary circumstances has no difficulty in adapting itself to changes of temperature, but if these are varied beyond the point at which its capacity of adjustment begins to fail—for example, during an extreme winter—the organism being unable to meet the condition must perish. The human organism, on the other hand, can respond to this external condition, as well as to countless other vicissitudes under which lower forms would inevitably succumb. Man's adjustments are to the largest known area of Environment, and hence he ought to be able furthest to prolong his Life.

It becomes evident, then, that as we ascend in the scale of Life we rise also in the scale of longevity. The lowest organisms are, as a rule, shortlived, and the rate of mortality diminishes more or less regularly as we ascend in the animal scale. So extraordinary indeed is the mortality among lowly-organized forms that in most cases a compensation is actually provided, nature endowing them with a marvellously increased fertility in order to guard against absolute extinction. Almost all lower forms are furnished not only with great reproductive powers, but with different methods of propagation, by which, in various circumstances, and in an incredibly short time, the species can be indefinitely multiplied. Ehrenberg found that by the repeated subdivisions of a single Paramecium, no fewer than 268,000,000 similar organisms might be produced in one month. This power steadily decreases as we rise higher in the scale, until forms are reached in which one, two, or at most three, come into being at a birth. It decreases, however because it is no longer needed. These forms have a much longer lease of Life. And it may be taken as a rule, although it has exceptions, that complexity in animal organisms is always associated with longevity.

It may be objected that these illustrations are taken merely from morbid conditions. But whether the Life be cut short by accident or by disease the principle is the same. All dissolution is brought about practically in the same way. A certain condition in the Environment fails to be met by a corresponding condition in the organism, and this is death. And conversely the more an organism in virtue of its complexity can adapt itself to all the parts of its Environment, the longer it will live. "It is manifest a priori," says Mr. Herbert Spencer, "that since changes in the physical state of the environment, as also those mechanical actions and those variations of available food which occur in it, are liable to stop the processes going on in the organism; and since the adaptive changes in the organism have the effects of directly or indirectly counterbalancing these changes in the environment, it follows that the life of the organism will be short or long, low or high, according to the extent to which changes in the environment are met by corresponding changes in the organism. Allowing a margin for perturbations, the life will continue only while the correspondence continues; the completeness of the life will be proportionate to the completeness of the correspondence; and the life will be perfect only when the correspondence is perfect." [1]

[1] "Principles of Biology," p. 82.

We are now all but in sight of our scientific definition of Eternal Life. The desideratum is an organism with a correspondence of a very exceptional kind. It must lie beyond the reach of those "mechanical actions" and those "variations of available food," which are "liable to stop the processes going on in the organism." Before we reach an Eternal Life we must pass beyond that point at which all ordinary correspondences inevitably cease. We must find an organism so high and complex, that at some point in its development it shall have added a correspondence which organic death is powerless to arrest. We must, in short, pass beyond that finite region where the correspondences depend on evanescent and material media, and enter a further region where the Environment corresponded with is itself Eternal. Such an Environment exists. The Environment of the Spiritual world is outside the influence of these "mechanical actions," which sooner or later interrupt the processes going on in all finite organisms. If then we can find an organism which has established a correspondence with the spiritual world, that correspondence will possess the elements of eternity—provided only one other condition be fulfilled.

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."