The circularity becomes specially glaring when put in the following way: The changes of things are changes in Time; but the change of events or of moments from future, through present, to past, is a change of Time, people hardly expect to reduce changes of Time to changes in Time, since Time would then need another Time to change in. Duration in Time corresponds to extension in Space. Now, just as people never perceive points or even unextended particles, so people are never aware of moments or of momentary events. The most general kinds of relation between finite events are those of partial precedence and partial subsequence; the rest can be defined in terms of these. From these crude perceptible data and their crude perceptible relations the concepts of momentary events and moments can be obtained, and their exact relations determined, by the Method of Extensive Abstraction.