It is none the less a necessary phenomenon, for it is involved in the idea of a continuous gradation of monads, in the distinction between the infinite and the finite, or, as Leibniz often prefers to put it, between the "creator" and the "created." There is involved everywhere in the idea of Leibniz the conception of subordination; of a hierarchy of forms, each of which receives the law of its action from the next higher, and gives the law to the next lower. We have previously considered the element of passivity or receptivity as relating only to the monad which manifests it. It is evident, however, that what is passive in one, implies something active in another. What one receives, is what another gives. The reciprocal influence of monads upon one another, therefore, as harmonious members of one system, requires matter. More strictly speaking, this reciprocal influence _is_ matter. To take away all receptivity, all passivity, from monads would be to isolate them from all relations with others; it would be to deprive them of all power of affecting or being affected by others. That is what Leibniz meant by the expression already quoted, that if monads had not matter as an element in them, "they would be, as it were, deserters from the general order." The note of unity, of organic connection, which we found to be the essence of the Leibnizian philosophy, absolutely requires, therefore, matter, or passivity. It must be remembered that this reciprocal influence is ideal. As Leibniz remarks, "When it is said that one monad is affected by another, this is to be understood concerning its _representation_ of the other. For the Author of things has so accommodated them to one another that one is said to suffer (or receive from the other) when its relative value gives way to that of the other." Or again, "the modifications of one monad are the ideal causes of the modifications of another monad, so far as there appear in one the reasons on account of which God brought about in the beginning certain modifications in another." And most definitely of all: "A creature is called active so far as it has perfection; passive in so far as it is imperfect. One creature is more perfect than another so far as there is found in it that which serves to _render the reason_, _a priori_, for that occurring in the other; and it is in this way that it acts upon the other."