Only intellect can examine itself. The stone falls, but knows not that it falls; the ray calcines and pulverizes, ignorant of its power; the flower knows not that its beauty is enchanting; and the brute beast follows his instincts, but asks not the reason of them. Man alone, a fragile organization, appearing for a moment on earth again to return to the dust, harbors a spirit, which first inspects the external world, and then, anxious to ascertain its own nature, enters into itself as into a sanctuary, and becomes its own oracle. What am I? What do I do? What do I think? What phenomena do I experience within myself? Why am I subject to them? What is their cause, their order of production, their relations? The mind asks itself these questions,--serious and difficult indeed, but noble and sublime questions; an unfailing proof that there is within us something superior to inert matter susceptible only of motion and a variety of forms, that there is something, which, by an internal activity, spontaneous and rooted in our very nature, presents us an image of that infinite Activity, a single act of whose will created the world from nothing.(1) CHAPTER II. TRUE STATE OF THE QUESTION. 5. That we have certainty, common sense assures us, but what is its basis, and how it is acquired, are two difficult questions, which it is for philosophy to answer. Three very different questions are involved in that of certainty; and if confounded, they contribute not a little to the creation of difficulties, and the confusion of matters which, even when they have their various aspects most accurately marked, are sufficiently hard and complicated. It will greatly conduce to the due determination of our ideas, carefully to distinguish between the existence of certainty, its basis, and the mode in which it is acquired. Its existence is an indisputable fact; its basis the object of philosophical researches, and the mode of acquiring it frequently a concealed phenomenon not open to observation. 6. That bodies exist is a fact that no man of sane mind can doubt. No questions raised upon this point can ever shake our firm conviction in the existence, without us, of what we call the corporeal world. This conviction is a phenomenon of our existence. Explain it, perhaps we cannot; but we certainly cannot deny it; we submit to it as to an inevitable necessity. What is the basis of certainty? Here we have not a simple fact, but a question solved by every philosopher in his own way. Descartes and Malebranche recur to the veracity of God; Locke and Condillac to the peculiar character and evolution of certain sensations.