The only remark made by Dr. Porter which has a direct bearing on this important discussion is that "Space and time are neither relations nor correlations, but _correlates_ to beings and events" ("The Human Intellect," p. 568). It may seem an act of presumption in one who has spent much less time on these studies than Dr. Porter to offer a criticism on this final deliverance. But when he tells us that space and time are neither relations nor correlations, after having through four pages "On the relations of space and time concepts to motion" labored to sustain the doctrine of Trendelenberg that "the categories of space and time are derived from the universal and all-pervading motion which is common to both" (p. 526), we confess we are amazed. Let it be granted that the spatial and temporal relations can be, in their last analysis, resolved into motion, still the question remains, How can we conceive of motion except as the result of force?--that is, of power actually exerted somewhere. In the last analysis, therefore, the relations of space, time, and motion are resolved into "_the relation of causality_." The conclusion seems inevitable that time and space are _correlations of finite existences_. Annihilate all finite existences and finite duration, and there is neither space nor time--that is, there is "pure nothing." Or, more properly, there is the Omnipotence, the Immensity, the Eternity of God, whose causation may give existence to finite beings with all their necessary as well as contingent relations. "Whoever maintains a beginning of the world must also adopt _a beginning of time_, for only worldly being, which according to its notion has not its ground in itself, but is an originated being, can at all have time for the form of its existence."[110] And now, in summing up, let us see if we can clearly disengage three classes of distinct notions: 1. The notion of concrete and finite EXTENSION as the essential quality of matter; and the notion of finite DURATION as a quality of changeful dependent existence. 2. The notion of SPACE as the relation of co-existing material things--that is, the relation of position, distance, direction, hereness, thereness; and the notion of time as the relation of successive existence--that is, the relation of priority and posteriority, of past, present, and future. 3. The notion of IMMENSITY and ETERNITY--that is, an absolute continuity and illimitability of being, the absence of all limit, all quantity, all beginning and end, the attributes of the unconditioned Being. Let us endeavor sharply to define these notions, which unhappily are too often confounded.