On the other hand there is a wavering treatment of the nature of spirit. At times it is treated as precisely on a level in kind with the monads that "compose" matter, differing only in the greater degree of its activity. But at other times it is certainly represented as standing on another plane. "The difference between those monads which express the world with consciousness and those which express it unintelligently is as great as the difference between a mirror and one who sees." If Leibniz means what he seems to imply by these words, it is plainly asserted that only the spiritual being is worthy of being called a monad, or individual, at all, and that material being is simply a dependent manifestation of spirit. Again he says: "Not all entelechies are, like our soul, _images of God_,--being made as members of a society or state of which he is chief,--but all are _images of the universe_." In this distinction between self-conscious beings as images of God and unconscious monads as images of the universe there is again implied a difference of kind. That something is the image of the universe need mean only that it cannot be explained without its relations to the universe. To say that something is the image of God, must mean that it is itself spiritual and self-conscious. God alone is reason and activity. He alone has his reality in himself. Self-conscious beings, since members of a community with him, must participate in this reality in a way different in kind from those things which, at most, are only substances or objects, not subjects. Nor do the difficulties cease here. If matter be conceived, not as implied in the relations by which reason is realized in constituting the universe, but as itself differing from reason only in degree, it is impossible to account for its existence. Why should a less degree of perfection exist than is necessary? Why should not the perfect activity, God, complete the universe in himself? Leibniz's answer that an infinity of monads multiplies his existence so far as possible, may hold indeed of other spirits, who mirror him and live in one divine society, but is utterly inapplicable to those which fail to image him. Their existence, as material, is merely privative; it is merely the absence of the activity found in conscious spirit. How can this deprivation, this limitation, increase in any way the harmony and perfection of the universe? Leibniz's theory of the negative, in fine, compels him to put nature and spirit on the same level, as differing only in degree. This, so far from giving nature a reality, results in its being swallowed up in spirit, not as necessarily distinct from it and yet one with it, but as absorbed in it, since the apparent difference is only privative. Nor does the theory insure the reality of spirit. This, since one in kind with matter, is swallowed up along with it in the one substance, which is positive and self-identical,--in effect, the _Deus sive Natura_ of Spinoza.