conclusions? Has there, for example, been since the days of Plato a single metaphysician who has denied the knowledge of the senses to be relative, and has the full scope and bearing of this principle been accurately measured? Can that be denied which has been scientifically demonstrated, which Descartes already affirmed, _i.e._, that light and sound--Nature's two great languages--are only the products of our physical organization, and that outside of the eye that sees, and the ear that hears, there is nothing external to us but a series of vibrations and undulations, which are neither luminous nor sonorous? Reduced to itself, without the presence of men or animals, matter is merely darkness and silence! What sort of matter may this be, and how little resembling the one we know? But is not, it may be said, the reality of that matter attested at least by resistance, by impact? The reality--yes; but is the very nature of the external thing, as it is in itself, manifested thereby? What is impact, what is resistance, if not a mode of our sensations? To be assured of this, we have but to turn to all that metaphysicians teach us as to the nature of God. All agree in saying that God has no sensations. If God be cognizant of matter, as is indubitable, it follows that He does not know it through sensations similar to ours. The _argumentum baculinum_ which appears so convincing to Sganarelle, would be powerless with regard to a pure spirit, still more an infinite spirit. Now is not this as much as to say that impact is the mode of action bodies exercise on each other, and by which sentient beings are made aware of their existence, but that it is a mode purely relative to the sensibility of finite beings? Say that, we at least admit with Descartes the reality of extension. But what is the real size of the extended things by which we are surrounded, and which according to the shape of our lenses we see enlarged, diminished, or even distorted in a thousand ways? Were it to please God, as Leibnitz has said, to collect the immensity of worlds into a walnut-shell, while preserving the proportion of objects, we should never find it out; and such diminution might be carried on infinitely, without ever reaching any term of smallness. 'We grant it,' will be the reply--'all sensible knowledge is relative; Plato, Malebranche, Leibnitz, have sufficiently told us this; but above the senses there is the understanding, which alone is made for truth. Our senses give us the appearance of things, our understanding makes us see them as they are in themselves.' Nothing more true, and this is the basis of metaphysics. But the question is, to what point the understanding is separated and separable from sensibility, and reciprocally, to what point sensibility enters into the understanding. Is there anything in us which can really be called understanding pure? Understanding--yes; but pure--no! Man cannot think without images, says Aristotle; this alone demonstrates that our