W e have now to raise the same kind of questions about date and duration as we have just been raising about place and shape. As in the last chapter we were learning something fresh, not only about Matter, but also about Space, so here we are going to dig beneath the traditional concepts of Time and Change which were treated in Chapter II. W e shall also be correcting certain simplifying assumptions which were made in the last chapter, such, e.g., as the assumption that our successive sensible fields are literally momentary.