 According to Berlin, philosophy concerns itself with questions of a special, distinctive character. To such questions not only are the answers not known, but neither are the means for arriving at answers, or the standards of judgement by which to evaluate a suggested answer. Thus the questions ‘How long does it take to drive from x to y?’ or ‘What is the cube root of 729?’ are not philosophical; while ‘What is time?’ or ‘What is a number?’ are. ‘What is the purpose of human life?’ or ‘Are all men brothers?’ are philosophical questions, while ‘Do most of such-and-such a group of men think of one another as brothers?’ or ‘What did Luther believe was the purpose of life?’ are not.