I end with a word on the new symbols which I have employed. Most writers on logic strongly object to all symbols. . . I should advise the reader not to make up his mind on this point until he has well weighed two facts which nobody disputes, both separately and in connexion. First, logic is the only science which has made no progress since the revival of letters; secondly, logic is the only science which has produced no growth of symbols.
Of all the intellectual faculties, judgment is the last to mature. A child under the age of fifteen should confine its attention either to subjects like mathematics, in which errors of judgment are impossible, or to subjects in which they are not very dangerous, like languages, natural science, history, etc.
Faith gives the courage to live and do. Scientists, with their disciplined thinking, like others, need a basis for the good life, for aspiration, for courage to do great deeds. They need a faith to live by. The hope of the world lies in those who have such faith and who use the methods of science to make their visions become real. Visions and hope and faith are not part of science. They are beyond the nature that science knows. Of such is the religion that gives meaning to life.