Our manner of life will have to be modified and directed according to rational and scientific data if we are to run through the normal cycle of life—orthobiosis. The pursuit of that goal will even influence the basis of morals. Orthobiosis cannot be accessible to all until knowledge, rectitude, and solidarity increase among men, and until social conditions are kinder.
Man will then no longer be content with his natural inheritance; he will have to intervene actively in order to correct his disharmonies. “Even as he has modified the nature of plants and animals Man will have to modify his own nature in order to make it more harmonious.”
In order to obtain a new race, one forms an ideal in relation to the organism to be modified. “In order to modify human nature, it is necessary to realise what is the ideal in view, after which every resource of which Science disposes must be taxed in order to obtain that result. If an ideal is possible, capable of uniting men in a sort of religion of the future, it can only be based on scientific principles. And if it is true, as is so often affirmed, that it is impossible to live without faith, that faith must be faith in the power of Science.”
In those words, Metchnikoff ends his book on Human Nature.
The public at large and many critics did not understand the deep and general meaning of Metchnikoff’s thoughts. They reproached him with having an insufficiently exalted ideal, for they only saw in his doctrine the desire of postponing senility and living longer. They did not understand that to revolt against the lack of harmony in nature, through which all humanity has to suffer, not only physically but morally, was to aspire to perfection. They did not consider that, in order to attain that end, all human culture and the whole social state would have to be modified; that this could only be done through many virtues, intense energy, and great self-control. They had not understood the elevation and power of an ideal which aspired to perfect not only the direction of life but human nature itself. They had not understood the audacious beauty of such a struggle, the benefit conferred by the belief that the human will and the human mind are capable of transforming Evil into Good according to a conceived ideal!...
In the meanwhile Metchnikoff, convinced that Knowledge is Power and that “Science alone can lead suffering Humanity into the right path,” quietly continued his task.
One of the most characteristic symptoms of old age is the hardening of the arteries—arterio-sclerosis. He therefore especially wished to elucidate the mechanism of that phenomenon.
Whilst many, yet unknown, factors come into play in senility, one disease, syphilis, often provokes arterio-sclerosis, indisputably due to a morbid agent. Metchnikoff therefore began to study this disease, of which the origin is infectious—especially as he thought he could do so experimentally.