We all of us say, when we are bored, that "the time passed slowly" or, when we are happy and amused, that "the time flew" and although this may appear at first sight to be no more than a loose way of speaking I think that there is more in it than that. It is here, in fact, that we find what I can only call a "check" on the measurement of time. It is the apprehension of something capable of undergoing change, of Psychic states to wit, whose changes are yet totally independent of the spatial changes by which we ordinarily measure time. A man who is hanging by a frayed rope over a precipice waiting for someone to come and rescue him might very likely say that "It seemed hours" although it might really have been no more than a very few minutes. Yet in one sense he might be speaking the literal truth. The changes which took place in his mental states during those few minutes might well be as complex and extensive as those he would normally experience in the course of hours. This should suffice to make clear the difference between the "real time process" which we measure and the recurrence of spatial simultaneities by which we measure it. If we consider the latter alone we soon find that they are difficult of comprehension. As Mr. Lindsay says in his book "The Philosophy of Bergson," p. 128. "If we eliminate real time altogether we get a number of simultaneities whose relation to each other we cannot understand.... For the relation between the simultaneities is taken to be that of the parts to the whole, but ... that is itself a simultaneity ... the relation of the simultaneities which are now taken as in their aggregate constituting change must be conceived of as necessary, as somehow all existing at once." And again: "We can only understand change by realising that it is incapable of spatial expression...." This quotation seems to me to be important because it brings out clearly the points with regard to which I think that the higher space hypothesis may be important. For although I am entirely in accord with the idea that there are, so to speak, two sorts of time I feel that in the light of the hypothesis we cannot allow the statement that "change is something which is incapable of spatial expression" to pass unchallenged. If it were put in the form, "material change is incapable of expression in terms of space of three dimensions," I should have nothing to say. But in the course of my remarks on the phenomena of change in a two-dimensional world, I pointed out that it is possible to integrate an infinite number of three-spatial simultaneities into a four-dimensional whole. The introduction of this concept seems to me calculated to modify the whole aspect of the question. For, by its light, we see that all the three-spatial simultaneities by which we mark time _can_ exist at once.