92. In order that this hypothetical value of ideas may be converted into a positive value, nothing is necessary but that the condition involved in the general proposition: "Every contingent being must have a cause," be verified. Of itself alone this teaches us nothing concerning the real world; but from the moment that experience shows us a single contingent being, the general proposition, before sterile, becomes exceedingly fruitful. So soon as experience shows us a contingent being, we know the necessity of its cause; we also infer the necessity of the proportions, which the activity producing must preserve with the thing produced; knowing the qualities of the latter, we infer those which ought to be found in the former. In this manner, resting upon two bases, one of which is ideal truth and the other real truth, or data supplied by experience, we construct a true positive science referred to determinate facts. 93. Since the being that thinks necessarily has consciousness of itself, no thinking being can be limited to the cognition of purely ideal truths. Even if we were to suppose it perfectly isolated from all other beings, in absolute non-communication with every thing not itself, so as neither to exert any influence upon them, nor to be influenced by them, it could not be reduced to the cognition of a purely ideal order; for, by the very fact that it is thinking, it is conscious of itself, and consciousness is essentially a particular fact, a cognition of a determinate being, since without it there could be no consciousness. 94. This observation overturns to its very foundation the system which pretends to bar all communication between the real and ideal orders. It shows also that experience is not only possible, but absolutely necessary to every thinking being, since consciousness is by its very nature an experience, and the clearest and surest experience. The truths of the ideal order are then necessarily interlinked with those of the real order: to suppose all intercommunication between them impossible, is to disown a fundamental fact of ideological and psychological science, consciousness.