Mr. Martineau admits that the assumption of "the coeval existence of matter as the condition and medium of the Divine agency" "rests on quite other grounds than those which support our belief respecting space."[65] We can conceive the non-existence of matter, but we can not conceive the non-existence of space. The idea of space is absolutely necessary, therefore "no one asks a cause for the space of the universe."[66] In making this assertion, however, Mr. Martineau betrays some want of acquaintance with the history of the philosophy of space and time. Many able and thoroughly philosophic minds have "asked a cause," and have assigned a cause for "the space of the universe." Sir Isaac Newton held that "God endures always and is present every where, and by existing always and every where _constitutes_ duration and space."[67] This doctrine, thus generally stated, is held by Saisset to be incontestible.[68] McCosh also believes that time and space are not independent of God: "I am not necessarily obliged to believe that the infinity of space and time is independent of the infinity of God.... Who will venture to affirm that space and time, being dependent on God, may not stand in some relation to God which is altogether indefinable and utterly incomprehensible by us."[69] Finally, Schleiermacher and Nitzsch do not hesitate to teach that "God is the all-mighty cause of space" and "the efficient cause of time."[70] The question whether the idea of space is conditionally or unconditionally necessary can only be determined by the solution of the deeper question whether space is a real entity or a relation. If space is a real entity, it must have properties or attributes, but what philosopher of any reputation has ever attempted to set down the properties or attributes of space? They who assert that space is an uncreated, independent, and indestructible entity, ought to be able to define it and tell _what_ it is. Dr. Porter tells us that space can not be defined, "We can not form a concept of this _entity_ by means of generalized attributes or relations."[71] Can that be for us an entity of which we can form no concept, and which we can not determine in thought by any attribute or relation? The writer of the article on "The Philosophy of Time and Space," in the _North American Review_,[72] is an earnest defender of the objective reality of space as an independent and indestructible entity, and he has defined and analyzed the concept. "Space is _absolute vacuity_" (p. 91). "The idea of space is a triple synthesis ... of three _negative_ notions--receptivity, unity, and infinity; the first is the negation of matter, the second is the negation of divisibility, the third is the negation of limitation" (p. 95). Do these words convey any knowledge? Absolute vacuity is void, empty, inane. Absolute vacuity is pure nothing, and of course there is nothing to be divided and nothing to be limited. Absolute vacuity is a