Leibniz profoundly influenced the course of what we may term "animistic" thought by his doctrine of monads. Whereas Descartes had defined substance as extension, Leibniz conceived it as activity, or active force, and as divided up into an infinite number and variety of individual centres, each with its own force or life, and, up to a certain point, each with its own consciousness. All beings are thus essentially akin, but differ in the grades of consciousness to which they attain. But since consciousness depends on organisation, and since organisation is constantly developing, there is continuous progress. Each individual monad develops from within by virtue of a spiritual element which it possesses--that is to say, not mechanically, but from an internal principle, implying sensation and desire. These monads, when looked at from without, are grouped together into various extended objects. If we ask Leibniz how such inwardly developing centres are combined together into a universe, his reply is that God has so ordered things that each monad develops in definite relation to all the rest; they all keep time, like clocks with different works, springs, pendulums, but regulated to mark simultaneously each period of time as it passes. This is the famous theory of pre-established harmony. This doctrine grants the nature-mystic all he needs, but in an artificial way which fails to carry conviction. The universe is split up into isolated units which have no real connection with each other save through ideas in the mind of God. Communion with nature, however, should be more direct and more organic than that effected by a pre-established harmony. Is it possible to retain the strong points of the theory while securing organic interpenetration of all modes of existence? Lotze, for one, deemed it possible. Here is an interesting and typical passage from his "Philosophy of Religion." "If it is once held conceivable that a single supreme intelligence may exert an influence on the reciprocal relations of the elements of the world, then similar intelligence may also be imagined as immediately active in all these individual elements themselves; and instead of conceiving them as controlled merely by blindly operative forces, they may be imagined as animated spiritual beings, who strive after certain states, and offer resistance to certain other states. In such case there may be imagined the gradual origin of ever more perfect relations, from the reciprocal action of these elements, almost like the reciprocal action of a human society; and that too without necessarily arriving at the assumption to which we are here inclined, of a single, supreme, intelligent Being. Our reasoning issues rather in a sort of polytheistic or pantheistic conception, and that too in quite tolerable agreement with experience."