Does life have meaning? Are there objective ethical truths? Do we have free will? What is the nature of our identity as selves? Must our knowledge and understanding stay within fixed limits? These questions moved me, and others, to enter the study of philosophy. I care what their answers are. While such other philosophical intricacies as whether sets or numbers exist can be fun for a time, they do not make us tremble.

Robert Nozick, Philosophical Explanations, Cambridge, Massachusetts, 1981, p. 1