Life has a third tendency, much less easy to verify but just as fundamental as the other two. This is the upward trend of mind in the course of the evolution of living creatures. Paleontology, like history, is only a conjectural science. Its data are few and often highly uncertain. Since it is far from possessing the precision of chemistry or physics, we cannot hope that it will give us an exact knowledge of our forefathers. Nevertheless it offers us documents of undoubted value about our past. Considered in broad outline, the evolution of living things is an established fact. Mind only manifested itself as distinct from matter after a long ascent through the animal forms which succeeded each other, from the amoeba to man, on the surface of our planet

Perhaps it was already present on earth before the appearance of life. Perhaps it was already implicit in the creative idea which was progressively realized in unicellular crea-tares, invertebrates, fish, amphibians, reptiles and finally warm-blooded animals. Claude Bernard wrote: "The governing idea of this vital evolution belongs essentially to the realm of life and not to chemistry, physics or anything else." In this aspect plants and trees resemble animals. Is there not a creative idea in the acorn which develops little by little and manifests itself fully in the oak? It seems that the development of the species, like that of the individual, comes about through the impetus of an immanent force which has some analogy with thought. But this thought is very different from human thought, being at once blind and clear-sighted, lavish and thrifty, hesitant and assured. Mind was incapable of manifesting itself in the world under the aspect we know it today until living matter had acquired an appropriate structure. The realization of this structure demanded a preparation which lasted perhaps a thousand million years. Then, side by side with the gigantic and stupid dinosaurs with their rudimentary brain, appeared small, intelligent, alert animals whose blood had a constant temperature. The rapid progress of cerebral matter began with the first mammals, probably forty to fifty million years ago. This was an immensely significant event, for a certain degree of perfection of this brain substance was indispensable to the appearance of mind in living matter. Paleontology gives us a very incomplete picture of our history. The documents on which the doctrine of evolution is based are few in number. It is possible that the missing links in the chain will never be brought to light by new discoveries.

Perhaps even the proofs of our descent from an ancestor whom we have in common with the anthropoid apes do not exist. Nevertheless, it is certain that the brain was perfected irregularly, discontinuously but progressively through the animal series over millions of years. From the rudimentary aspect it presented in the lower animals such as the medusa, the nervous system arrived at extreme complexity in the mammal. It was particularly complex in the tarsier which some paleontologists consider as our probable ancestor. The brains of the marmoset, the monkey and the anthropoid ape show an enlargement in the centers of sight, touch and the movements of the extremities. Though the relations between the brain and the mind are far from being fully known, we do know that mind depends on the quantity and quality of the substance of the brain and on the endocrine glands. It is also certain that intelligence does not depend only on the volume of the brain, for the brain of some idiots is as large as that of Napoleon. Relative to its own weight, the mouse possesses a brain heavier than man's, yet the mouse is not more intelligent. On the other hand the volume of the nervous substance in reptiles, dinosaurs and birds was small in comparison with that of the other tissues. It becomes much greater in mammals and above all in primates. In spite of the gropings, the stops and the sudden leaps of evolution, brain and intelligence continued to develop simultaneously. During the Miocene period, perhaps twenty or thirty million years ago, there were already great anthropoids in the forests of Europe whose cranial capacity was no less than that of gorillas existing today. The brain of a gorilla weighing more than 300 kilograms does not exceed 600 cubic centimeters. At the end of the Pliocene period appeared a phenomenon of immense importance. This was the rapid growth of the brain in creatures which in some ways resembled the anthropoid of the Miocene period. One of the first creatures whose cerebral volume was clearly superior to that of the other primates lived in Java, possibly five hundred thousand years ago. This was Pithecanthropus, whose cranial capacity was roughly 900 centimeters and whose facial angle was 52 degrees. Some hundreds of thousands of years before him there was, in Sussex, a still more intelligent being; the Ecanthro-pus of Piltdown whose cerebral volume was nearly 1,350 cubic centimeters. This creature could already roughly fashion flint into tools and weapons. It was probably about the same time that the Sinanthropus, or man of Peiping, flourished. Much later, after the fourth ice age, perhaps forty thousand to one hundred thousand years before the Christian era, appeared Neanderthal man. This stocky little creature, with its short, powerful neck, still had the appearance of an anthropoid. He lived in Germany, near Dusseldorf, and also in the valley of the Dordogne in France. He manufactured very beautiful flint tools. His facial angle varied from 58 degrees to 67 degrees. His cranial capacity, about 1,550 cubic centimeters, equaled that of the present inhabitants of Europe. About twenty or thirty thousand years ago, he gave place, as we know, to Cro-Magnon man whose highest facial angle was 65 degrees and whose powers of observation, aesthetic sense and manual skill were probably not inferior to own own.

Mind arose slowly through a series of animal forms in the course of hundreds of millions of years. Then, hardly two thousand centuries ago, from the beginning of the Pleistocene era, this rise was greatly accelerated. In spite of geological convulsions, repeated freezing of the earth's surface, attacks of formidable prehistoric animals, famine and disease, man automatically continued his journey toward the light. He made weapons and tools; he discovered fire; he invented the wheel; he cultivated grain; he domesticated wild animals. And, when his intelligence and his inventions had procured him some leisure, he began to reflect on the nature of things, of himself, of the universe and of God. In the fortieth century B.C., the Egyptians already possessed a written code of morals. According to the Canon of Confucius, the Chinese astronomers of the twenty-fourth century determined the summer and winter solstices and approximately calculated the length of the year. A century later, the Emperor Shun offered prayers and sacrifices to a single God. Finally, in the sixth century, with the philosophers of the Ionian School, Thales, Anaximander and Anaximenes, came the dawn of our own civilization.

Thus, over a space of time no longer in the history of living beings than one hour in the life of a man, mind emerged from matter and installed itself on our planet. From that moment it continued its ascent in two distinct, though complementary directions. It took the road of intellect, the creator of philosophy and science, and the road of feeling, that is to say of art, religion and morality.