Leibniz, recognizing that reality is an organic whole,--not two parts with a chasm between them,--says that "God does not arbitrarily give substances whatever qualities may happen, or that he may arbitrarily determine, but only such as are natural; that is, such as are related to one another in an _explicable_ way as modifications of the substance." Leibniz feels sure that to introduce the idea of the inexplicable, the purely supernatural, into the natural is to give up all the advantages which the modern mechanical theory had introduced, and to relapse into the meaningless features of scholasticism. If the "supernatural"--that is, the essentially inexplicable--is introduced in this one case, why should it not be in others; why should we not return outright to the "fanatic philosophy which explains all facts by simply attributing them to God immediately or by way of miracle, or to the barbarian philosophy, which explains phenomena by manufacturing, _ad hoc_, occult qualities or faculties, seemingly like little demons or spirits capable of performing, without ceremony, whatever is required,--as if watches marked time by their horodeictic power, without wheels, and mills ground grain, without grindstones, by their fractive power"? In fact, says Leibniz, by introducing the inexplicable into our _explanations_ "we fall into something worse than occult qualities,--we give up philosophy and reason; we open asylums for ignorance and laziness, holding not only that there are qualities which we do not understand (there are, indeed, too many such), but qualities which the greatest intelligence, if God gave it all the insight possible, could not understand,--that is, such as are _in themselves_ without rhyme or reason. And indeed it would be a thing without rhyme or reason that God should perform miracles in the ordinary course of nature." And regarding the whole matter of introducing the inconceivable and the inexplicable into science, he says that "while the conception of men is not the measure of God's power, their capacity of conception is the measure of _nature's_ power, since everything occurring in the natural order is capable of being understood by the created intelligence." Such being the thought of Leibniz regarding the virtual attempt to introduce in his day the unknowable into philosophy, it is evident that he must reject, from the root up, all theories of sensation which, like Locke's, make it the product of the inexplicable intercourse of two substances. For this doctrine, then, Leibniz substitutes that of an infinite number of substances, all of the same kind, all active, all developing from within, all conspiring to the same end, but of various stages of activity, or bearing various relations of completeness to the one end.