[Illustration: OLD LONDON BRIDGE, BEGUN BY PETER COLECHURCH IN 1176, AND FINISHED BY A FRENCHMAN, CALLED ISEMBERT, IN THE YEAR 1209] [Illustration: PONT SIDI RACHED AT CONSTANTINE, ALGERIA. BUILT IN 1908-1912 The span of the great arch is 70 metres. The work illustrates the longevity of custom and convention, being inspired partly by Roman aqueducts and partly by the two famous bridges over the Tech at Céret, in France, one of which dates from the year 1321. The span of its great arch is 45m. 45cm.] III CUSTOM AND CONVENTION Yet a pontist must be exceedingly careful when his tramps through any period bring him in touch with ethical problems. He should try to live on the highways of history, not in order to pass judgments on vice and on crime, but because he wants to see clearly, under the form of visual conception, why social concord and equity have never fared well, even the best forms of civilization being only half-educated barbarisms that allow their strife to be drilled by a vast number of active laws. These phases of compulsion go on increasing, yet they fail to resolve into harmony those rapacious egotisms that compete against each other in the body social like microbes in living tissues. As soon as a pontist understands his wayfaring through history, as soon as he feels at home in the general atmosphere of the human drama, he is glad to be a realist; then nothing that societies do or have done seems unexampled and inexplicable. To him, for example, the infanticide practised age after age by savage tribesmen is not more terrible than the death of babies in the slums of civilized towns, or than the degradation brought before his mind by the alert philanthropy that saves little English children from cruelties. To him, again, the slaughter on a great battlefield is not more woeful than the annual sacrifice of lives in street accidents, and railway smashes, and mine disasters, and sea tragedies; as well as in games and sports, in nursing the sick, and in all trades and professions. He is not scared by the fact that the sum of human life is war, but he is scared by the primordial customs and conventions that make the incessant war infinitely less humane than it could be and ought to be. So a pontist in his attitude to history is a sociologist, and not an abstract moralist. Each body social and its systems of circulation are to him what patients are to medical students in a hospital; he has to learn to be attentive to all disease and to make his diagnoses thoughtfully. Even then frequent mistakes will occur. One thing he must regard as his clinical thermometer: it is the truth that civilizations in their intercourse with right and wrong have been governed by habits and customs and conventions, which have caused most men to be other men; so that most human actions, whether studied in old history or in the current routine of living, are mere quotations