Like a motion picture. There is nothing difficult to grasp in that thought. We see a motion picture as a continuous flow of movement; but we know that in reality the seeming movement is merely a rapid change from one still picture to the next. So with all our Material Universe. It is as though Time, like a whirling knife-blade, were slashing through us--blotting us out, letting us live only in the progressive instants between the whirling blades. * * * * * "Time" is the factor of all this which we find most unnatural to envisage in its true aspect. I would have you imagine now, what I might term the physical aspect of Time. Consider it, for instance, as an all-pervading etheric fluid. Consider it strewn in a line from the Beginning to the End. Our minds are so limited that we must conceive everything in terms of tangibility--even the intangible. So I would have you picture Time as a stream of imponderable, invisible fluid. Imagine it in shape so that it could lie in some gigantic pipe--perfectly straight--of some inconceivable length. We put the Beginning and the End to bound it. This Time-fluid, then, you must picture as being at rest--the one thing of all things which does not move nor change. It lies there--forever. But do not forget this pipe-line of Time-fluid in which all this is happening! Let us cling to simple physical analogies. We must imagine, for instance, that the Time-fluid is progressively of different physical character along all its length from its Beginning to its End. Like water in a pipe--hot at one end, cold at the other, with every gradation of temperature in between. Or, to be just a trifle closer to fact, perhaps, the stream of Time might be imagined as a beam of light--red at one end and violet at the other--with every tint and shade merging along the way. Something then--like a Thought--is put into the pipe-line of Time at the Beginning. If you have conceived the fluid of Time as being hot at the Beginning--then imagine that this foreign, intangible substance which has been placed there is the same temperature. Because of that, let us say, it can remain there. But only for an instant! Because the foreign substance instantly desires to change its character. It desires, let us say, to become a bit cooler. It wants to reexist; to perpetuate itself in changed form. The fluid of Time at the Beginning will not tolerate anything cooler. Will not tolerate any change at all. So it shifts a changed replica of the restless thing along a bit. An event has occurred. A new thing exists, beside the old thing. Both lie there side by side--and the difference between their aspects is the change. Also, it is movement.