Extending these considerations to the whole of the phenomena known to us, Comte concludes in almost the same way as Cournot will later on. An order establishes itself in nature, since it subsists, since it is intelligible, since there are laws.[69] Does not the very idea of a law induce at once the corresponding idea of a certain spontaneous order? But “this consequence is not more absolute than the principle from which it is derived.”[70] The experience which reveals this order to us also shows us that it is imperfect, of an imperfection which grows with the complexity of phenomena. Every time that the necessary and sufficient conditions are realised for a natural system to be able to exist, this system exists in fact, however full of imperfections it may be in other respects. “Undoubtedly, an inevitable necessity which links together a series of events, and a premeditated plan which directs them, resemble each other very much so far as the consequences are concerned.”[71] But, if the necessity is established, there is no need to suppose the plan. Now the principle of the conditions of existence, in showing that all that is “indispensable,” is at the same time “inevitable,” renders this supposition superfluous. A double tendency makes itself felt in this theory. On the one hand Comte, faithful to the spirit of his philosophy, rejects all that claims to go beyond experience, that is to say the transcendental hypothesis of final causes and of optimism. On the other hand, he wishes to account for the order of nature, which is a fact. Now this order, all imperfect as it is, implies not only the existence of laws, but moreover a permanent harmony between these laws. “The present is full of the past, and big with the future.” The principle of the conditions of existence explains this permanence of order, at least as much as it needs to be explained from the positive point of view. For it states that everywhere, in fact, the dynamical laws are in harmony with the statical laws, and that “progress is a development of order.” The principle of the conditions of existence is no more _a priori_ than the principle of laws. Like it it is founded upon an “immense induction.” Like it again, it only acquires its full power when social science is created, and positive philosophy established. Should we not be tempted to see in this doctrine a kind of projection of an idealism such as that of Leibnitz on the lines of positive thought? Just as Leibnitz makes mechanism rest upon a deeper dynamism, so Comte completes the principle of laws by the principle of the conditions of existence. True, between these two doctrines there lies all the distance which separates the positive from the metaphysical spirit. But none the less both give symmetrical solutions of the same problem which correspond to one another, the one _a priori_ the other _a posteriori_. IV.