An evident order can be observed in the world. The sun never fails to rise. Night invariably succeeds day, and spring winter. Living beings, like inanimate ones, are constructed in a certain way and are definitely related to each other. Life conforms to its cosmic background and the cosmic background to life. All things found on earth and in the heavens are made up of the combination of less than one hundred elements. Though infinitely numerous, they are all related and each behaves in the mode ordained by its structure, for nature is incapable of caprice.

From time immemorial, men have been dimly aware of these facts. Long before the dawn of stoic thought, Hera-clitus had already grasped the idea of an order in the universe and the need to adapt ourselves to this order. Science was born of the belief that reality was essentially uniform. All research begins with an act of faith in the rational ordering of nature. The great success of science has proved that, far from being a superstition, such a belief was a pro-40 found and precise intuition of the structure of the cosmos. It is because there is nothing fantastic about the cosmos that science has been able to develop. Little by little, it has revealed the modes of behavior of the inanimate world and, to a certain extent, those of living beings. With Aristotle, it first described and classified phenomena. From qualitative, science then became quantitative. With Galileo, Newton and Lavoisier it came to its full stature.

Little by little, it perceived the hidden uniformity beneath the complex variety of the surface. It discovered the existence of constant relationships between varying phenomena. These relationships are natural laws: laws of matter, life and thought. The two last are far from being as simple as those which govern inert matter. They cannot yet be expressed in mathematical terms. Yet the leucocyte stretching out its pseudopods toward the bacterium, the wailing newborn baby and the scientist experimenting in his laboratory are no more due to a caprice of nature than tide, wind or avalanche. Investigated with scientific method, they all testify to the underlying order of things.

Natural laws differ profoundly from man-made ones. They are discovered, not invented. Like the spring at the bottom of the well, they exist before they are discovered. Our civil and military codes are mere collections of regulations. Natural laws express the very structure of things and constitute their functional aspect. Thus the function of the eye is to project the image of exterior objects on the extension of the brain which is inserted into it. Structure and function are two aspects of one and the same object. Natural laws are immanent in both animate and in-animate beings. If the substratum of the universe is a creative intelligence, they reveal an aspect of this intelligence. Marcus Aurelius thought the world was like the body of God. Too many human laws are, on the contrary, merely external. They represent only social conventions, frail and arbitrary products of our own reason. What is lawful in one country is not necessarily so in another. "Keep to the right," says the French highway code; "Keep to the left," says the English. In the sight of such laws, all men are by no means equal. The rich and powerful can infringe them with impunity. The natural laws, on the contrary, are universal and inexorable. In no country can they be disobeyed without penalty. Nor do they ever warn the transgressor; the punishment is as silent as the command.

On certain days of the year, the Athenian Assembly had the task of revising its laws. Social conventions are always transitory. But natural laws have existed since the origin of the universe and will last to its end. The speed of light will never change. Before the laws of gravity, all men are equal. We shall never be able, of our own accord, to walk on water or fly in air. As long as the moon circles the earth, there will be tides. Nothing will stop a chemical reaction from doubling its velocity each time the temperatures rises 10 degrees centigrade. Today, as one hundred thousand years ago, glycogene turns into lactic acid in a working muscle. When the muscle becomes acid, fatigue will supervene. A calorie will always equal 425 kilogram-meters. In the same way, the laws of heredity are invariable. Madmen and mental defectives will continue to be engendered by madmen and mental defectives. The tissues of human beings are of such a kind that they will always deteriorate under the influence of alcohol. Natural laws, then, do not, like civil law, constitute a contingent aspect of reality; they are a necessary aspect of everything which exists around us and in ourselves.

With a knowledge of these laws, we can predict phenomena or provoke their appearance at will. Such knowledge has made men masters of the earth. But order does not manifest itself so clearly in the whole of nature. Our mind cannot penetrate every realm of reality with equal ease. It excels in discovering the secrets of inert matter and in constructing mathematical abstractions. But, since it loves simplicity and life is infinitely complex, it finds it far harder to understand living phenomena. Mechanics, physics and chemistry are far more advanced than physiology, psychology or the social sciences. We understand atoms and stars better than our own minds.

There is a hierarchy in natural laws. At the top come those which express complete uniformity in the behavior of things. Such, for example, are the laws of gravity and of the conservation of matter and the two laws of the conservation and dissipation of energy. Lower down we find the biological laws such as those of adaptation and heredity. These are far from having reached that degree of abstraction, precision and beauty which enable the physical laws to be defined in algebraical formulas. They can only be considered as expressing the tendencies of certain bodily activities.

Even more imperfect are the laws of psychology. Yet the modalities of reason or feeling play as essential a part in the world as the law of gravity for they characterize the greatest and most mysterious energy on earth. On the lowest step of the hierarchy stand the laws of sociology. Many of these are mere hypotheses, for sociology is still a conjectural science. Thus we are far from knowing all the parts of reality with equal certitude.

Phenomena can only be predicted with certainty in the realm of physics or chemistry. We can foretell, without possibility of error, the exact moment of the next eclipse of the sun and what will happen if we mix sulphuric acid with carbonate of calcium. But we cannot determine in advance the time when a given individual will die or what effect victory or defeat will have on the future of a nation.

Perhaps human intelligence has not yet reached the period of evolution when it will become capable of grasping the real under its multiple forms. Perhaps we need only employ better and more patient methods for natural laws to reveal themselves with equal clarity in all domains. But our ignorance should not lead us to believe that order extends only to one part of the world.

Undoubtedly, the success of moral and social life depends on laws as definite, though more complex, as those which relate to the partial pressures of gases in mixtures or to the propagation of light rays. But we do not yet know those laws.

We must not forget that our ancestors divined an order in the universe, but that they never discovered its laws. The moderns have discovered the laws of physics, chemistry and physiology. Yet perhaps we shall remain forever incapable of formulating those laws of human relations whose existence we suspect today. In its slow ascent toward the light, the spirit only gradually acquires the strength to grasp the obscure mechanisms of the harmony of the world.