バートランド・ラッセル「幸福と熱意」* 原著：The Conquest of Happiness, 1930, chapter 11
本物の熱意は、－ 忘却を求めるようなものではないものであれば（嫌なことを忘れるための熱狂でないかぎり） －、人間生来の資質の一部である。幼児は見聞きする全てに興味を感じる。幼児にとって世界は驚きに満ちており、物事になじむことで身につく知識を常に熱心に探求する。外界への自然な興味を邪魔されない限り、人生は楽しい。・・・
In all these different situations the man who has the zest for life has the advantage over the man who has none. Even unpleasant experiences have
their uses to him. ...
Genuine zest, not the sort that is really a search for oblivion, is part of the natural make-up of human beings except in so far as it has been destroyed by unfortunate circumstances. Young children are interested in everything that they see and hear; the world is full of surprises to them, and they are perpetually engaged with ardour in the pursuit of knowledge, not, of course, of scholastic knowledge, but of the sort that consists in acquiring familiarity with the objects that attract their attention. ... Loss of zest in civilised society is very largely due to the restrictions upon liberty which are essential to our way of life.....
At every moment of life the civilised man is hedged about by restrictions of impulse: if he happens to feel cheerful he must not sing or dance in the street, while if he happens to feel sad he must not sit on the pavement and weep, for fear of obstructing pedestrian traffic. In youth his liberty is restricted at school, in adult life it is restricted throughout his working hours. All this makes zest more difficult to retain, for the continual restraint tends to produce weariness and boredom. Nevertheless, a civilised society is impossible without a very considerable degree of restraint upon spontaneous impulse, since spontaneous impulse will only produce the simplest forms of social cooperation, not those highly complex forms which modern economic organisation demands. In order to rise above these obstacles to zest a man needs health and superabundant energy, or else, if he has that good fortune, work that he finds interesting on its own account. Health, so far as statistics can show, has been steadily improving in all civilised countries during the last hundred years, but energy is more difficult to measure, and I am doubtful whether physical vigour in moments of health is as great as it was formerly.)