But these philosophies, as Professor Bergson especially among recent philosophers has pointed out,[4] gain whatever force they have principally from the fact that they think of time in terms of space. They picture it as a line already drawn, when they should picture it as a line in the process of being drawn. As already drawn, the line has a beginning, an end, and consequently, a middle point. Let us call the middle point the present. All the line to the left of that point we will call the past and all to the right of it the future. We thus behold time spatially with all its parts coexistent as the points on the line. Events are then conceived to move from the past through the present into the future, just as a pencil point may pass from the beginning of the line through its middle point to the end. But, unlike the pencil point, they can not go backward. This fact gives us a characteristic by which we may distinguish time from space even if we have represented time spatially. The spatial order is reversible, the temporal is not. Time is like a line on which you can go forward, but on which you can not go backward. But you can go forward. Everything goes from the past to the future. The present is but the transition point of their going. There are, undoubtedly, advantages in thinking of time in this spatial way. Thereby we are able to make calendars and have a science of mechanics. It affords a basis for many successful predictions. But, quite evidently, time is neither such a line nor anything like it. Nothing whatever goes from the past through the present into the future. We can not make such a statement intelligible. For "to go" from the past to the future is not like going from New York to Boston. Boston is already there to go to, but the future is not anywhere to go to. And New York is there to leave, but the past is not anywhere to leave. What then is this mysterious "going" if its starting-point and its end are both non-existent now? Clearly it is a "going" only in a metaphorical sense. We call it a "going" because we can so represent it by dates and places. We can say that here we have been going from Friday through Saturday to Sunday. But it is quite clear that to-day is neither past nor future, that it is neither yesterday nor to-morrow, and that if we go anywhere we must start to-day. When Sunday comes, Saturday will be yesterday. But note now the strange situation into which we have fallen--only in the future is this day ever in the past! And that is true of every day in the world's history. It becomes a past day only in its own future.