The purpose of the following article is to suggest certain problems, rather than to offer philosophical solutions of problems. I propose to state certain questions which are sometimes asked and to try to say both (a) why it is important that they should be asked, and (b) why, if we do ask them, we should endeavour to answer them as accurately as we can. A full discussion of what the true answers to the questions are will be beyond the province of this paper, and, if certain answers are suggested in passing, it will only be because it is difficult to make anything which consists of a mere sequence of questions at all interesting or readable.