On the other hand, Leibniz, as we saw in the earlier chapters, had learned positively from the growth of science, negatively from the failures of Descartes and Spinoza, to look upon the universe as a unity of inter-related members,--as an organic unity, not a mere self-identical oneness. Failing to see the cause of the failures of Descartes and Spinoza in precisely their adoption of the logic of identity and contradiction as ultimate, he attempted to reconcile this method with the conception of organic activity. The result is constant conflict between the method and content of his philosophy, between its letter and its spirit. The contradiction is a twofold one. The unity of the content of his philosophy, the conception of organism or harmony, is a unity which essentially involves difference. The unity of his method is a formal identity which excludes it. The unity, whose discovery constitutes Leibniz's great glory as a philosopher, is a unity of activity, a dynamic process. The unity of formal logic is exclusive of any mediation or process, and is essentially rigid and lifeless. The result is that Leibniz is constantly wavering (in logical result, not of course in spirit) between two opposed errors, one of which is, in reality, not different from Spinozism, in that it regards all distinction as only phenomenal and unreal, while the other is akin to atomism, in that attempting to avoid the doctrine of the all-inclusive one, it does so only by supposing a multitude of unrelated units, termed monads. And thus the harmony, which in Leibniz's intention is the very content of reality, comes to be, in effect, an external arrangement between the one and the many, the unity and the distinction, in themselves incapable of real relations. Such were the results of Leibniz's failure, in Kantian language, to criticise his categories, in Hegelian language, to develop a logic,--the results of his assuming, without examination, the validity of formal logic as a method of truth.