"From adolescence until the completion of Principia Mathematica, my fundamental preoccupation had been intellectual. I wanted to understand and to make others understand; also I wished to raise a monument by which I might be remembered, and on account of which I might feel that I had not lived in vain. From the outbreak of the First World War until my return from China, social questions occupied the centre of my emotions: the War and Soviet Russia alike gave me a sense of tragedy, and I had hopes that mankind might learn to live in some less painful way. I tried to discover some secret of wisdom, and to proclaim it with such persuasiveness that the world should listen and agree. But, gradually, the ardour cooled and the hope grew less; I did not change my views as to how men should live, but I held them with less of prophetic ardour and with less expectation of success in my campaigns. [My desire for children had] grown continually stronger, until it had become almost insupportable. When my first child was born, in November 1921, I felt an immense release of pent-up emotion, and during the next ten years my main purposes were parental. Parental feeling, as I have experienced it, is very complex. There is, first and foremost, sheer animal affection, and delight in watching what is charming in the ways of the young. Next, there is the sense of inescapable responsibility, providing a purpose for daily activities which skepticism does not easily question. Then there is an egoistic element, which is very dangerous: the hope that one's children may succeed where one has failed, that they may carry on one's work when death or senility puts an end to one's own efforts, and, in any case, that they will supply a biological escape from death, making one's own life part of the whole stream, and not a mere stagnant puddle without any overflow into the future. All this I experienced, and for some years it filled my life with happiness and peace."