It is useless to attempt, as we have done hitherto, to deduce these natural laws from philosophical principles or political and social ideologies. Such constructions, however ingenious, must always remain piecemeal views of human activity, pale phantoms of reality. Philosophy is always trying to make a harmonious synthesis of knowledge, to speculate on the origin and nature of things, and to formulate doctrines which will satisfy the aspirations of the soul. But such doctrines are like those luminous shapes which hover above a misty plain; no one can tell whether they are the eternal hills or merely clouds which the wind will soon disperse. No system of thought has yet gained universal adherence. Principles considered eternal by some are not admitted as such by others. Laws of life deduced from such principles are mere suppositions which can never have universal authority. The quarrel between materialists and idealists has been going on for twenty-five centuries and is far from being settled today. Is man matter or spirit or both at once? Are we to deduce the laws of life from the principles of Zeno or of Epicurus, from the ideas of St. Thomas Aquinas or from those of Jeremy Bentham? Is primitive life necessarily good and modern social life necessarily bad? "Everything is good as it comes from the hands of the author of life; everything degenerates in the hands of man," wrote Rousseau. In spite of the success of this doctrine, the noble savage remains a myth.
To the Utilitarians, the principle of the natural identity of interests appeared to be the fundamental law of economic relations. Today we know that these philosophers were wrong. Many men believe that the aim of life is the piling up of wealth; a few that it consists in laying up treasure in heaven "where neither rust nor moth doth corrupt." To put economics first, as Adam Smith and Karl Marx taught, involves rules of behavior opposed to those which derive from giving first place to the spiritual. Principles and controversies rage furiously about us. No system is suffi-ciently sure to serve as an indisputable base for our behavior. The laws of life can no more be deduced from eternal principles than can those of physics. We must renounce the hope that the logicians, however dexterous, can reveal the rules of human conduct
If we are not to deceive ourselves, we must deduce the laws of life from the observation of life itself, just as we have deduced the laws of physics and chemistry from observing inanimate matter. The time has come to corroborate philosophical principles by scientific concepts. Concepts derived from observation and experiment are solid and can be tested. In case of doubt, the observations and experiments which produced the concept can be repeated. Only an idiot would deny, for example, the existence of the laws of heredity and adaptation. Unfortunately, the study of man demands the knowledge of several exact techniques. To grasp human activities in all their complexity we need the methods of anatomy, physiology, physics, chemistry, pathology, medicine, pedagogy, psychology, economics and sociology. Before any phenomenon can be considered the expression of a fundamental mode of life, it has to be analyzed many times by different investigators and in different circumstances. The result of any one observation or experiment needs to be confirmed by others in the same country and also in other countries. The validity of a scientific hypothesis is far more severely tested than that of a philosophical principle. Thanks to a vast number of observations, we know that anyone transported from sea level to a high altitude shows symptoms of mountain sickness. After a few weeks, these symptoms disappear; the person has become acclimatized. Examination of the blood then shows that the red corpuscles have greatly multiplied. It is thus legitimate to deduce that the organism adjusts itself to the rarefaction of oxygen in the atmosphere by increasing the quantity of hemoglobin capable of stabilizing this gas. This brings to light many aspects of the law of adaption. Observation of the behavior of men in all epochs and all countries has shown that the human being who is not degenerate seeks at the same time freedom and discipline, activity and repose, adventure and security. This is an inherent characteristic of his nature, a law of his being. Only by observing that nature can we deduce its laws with any certainty since those laws are nothing but the fundamental modes of being, the essential trends and primordial needs of all men in all ages as they appear in the individual, in society and in the race.