95. To render the truth and exactness of the preceding doctrine more evident, let us suppose a man, or rather a human mind, absolutely ignorant of the existence of an external world, of every body, and even of every spirit; one that knows nothing concerning its own origin or destiny, but one that would nevertheless at the same time exercise its intellectual activity, without which it would be a lifeless thing, and could offer no field to observation. Let us suppose him to have general ideas, such as of being and of not-being, of substance and accidents, of the absolute and the conditioned, of the necessary and contingent. Manifestly he may combine them in various ways, and arrive at the same purely ideal results to which we ourselves arrive. There is no supposition more favorable to a series of abstract cognitions independent of experience, and yet not even in this case would the truths known be limited to the purely ideal order; it would even here be impossible for them not to descend to the real order, if the thinking being were not dispossessed of all consciousness of itself. Indeed, by the very fact that a being is supposed capable of thinking, it is supposed able to say to itself, _I think_. This act is eminently experimental, and it needs only to be united with general truths in a common consciousness, to enable the isolated being to rise above itself, and create for itself a positive science, by which to pass from the world of ideas to that of facts. The instability of its thoughts, and the permanence of the being that experiences them, offer to it a practical case in which the general ideas of substance and accident are particularized. The successive appearance and disappearance of its own conceptions will show to it the ideas of being and of not-being realized; the recollection of the time when its own operations commenced, beyond which the memory of its existence does not extend, will enable it to know the contingency of his own being; and this fact, combined with the general principles which express the relations between contingent and necessary beings, will suggest to the thought that there must be another that communicated to it its existence. CHAPTER XV. ILLUSTRATIONS OF THE VALUE OF GENERAL CONCEPTIONS.