[41] (1) We may add that the idea in the world of thought is in the same case as its correlate in the world of reality. (2) If, therefore, there be anything in nature which is without connection with any other thing, and if we assign to it a subjective essence, which would in every way correspond to the objective reality, the subjective essence would have no connection, [p] with any other ideas--in other words, we could not draw any conclusions with regard to it. (41:3) On the other hand, those things which are connected with others--as all things that exist in nature--will be understood by the mind, and their subjective essences will maintain the same mutual relations as their objective realities--that is to say, we shall infer from these ideas other ideas, which will in turn be connected with others, and thus our instruments for proceeding with our investigation will increase. (4) This is what we were endeavoring to prove. [42] (1) Further, from what has just been said--namely, that an idea must, in all respects, correspond to its correlate in the world of reality,--it is evident that, in order to reproduce in every respect the faithful image of nature, our mind must deduce all its ideas from the idea which represents the origin and source of the whole of nature, so that it may itself become the source of other ideas. [43] (1) It may, perhaps, provoke astonishment that, after having said that the good method is that which teaches us to direct our mind according to the standard of the given true idea, we should prove our point by reasoning, which would seem to indicate that it is not self-evident. (2) We may, therefore, be questioned as to the validity of our reasoning. (3) If our reasoning be sound, we must take as a starting-point a true idea. (4) Now, to be certain that our starting-point is really a true idea, we need proof. (5) This first course of reasoning must be supported by a second, the second by a third, and so on to infinity. [44] (1) To this I make answer that, if by some happy chance anyone had adopted this method in his investigations of nature--that is, if he had acquired new ideas in the proper order, according to the standard of the original true idea, he would never have doubted [q] of the truth of his knowledge, inasmuch as truth, as we have shown, makes itself manifest, and all things would flow, as it were, spontaneously towards him. (44:2) But as this never, or rarely, happens, I have been forced so to arrange my proceedings, that we may acquire by reflection and forethought what we cannot acquire by chance, and that it may at the same time appear that, for proving the truth, and for valid reasoning, we need no other means than the truth and valid reasoning themselves: for by valid reasoning I have established valid reasoning, and, in like measure, I seek still to establish it.