From the smallest reflection on the origin of our knowledge, it is easy to perceive that it is by comparison alone we acquire it. What is absolutely incomparable, is utterly incomprehensible; of this God is the only example; he exceeds all comprehension, because he is above all comparison. But whatever is capable of being compared, contemplated, and considered relatively, in different lights, may always come within the sphere of our understanding. The more subjects of comparison we have for examining any object, the more methods there are for obtaining a knowledge of it, and with greater facility. The existence of the soul is fully demonstrated. To be and to think are with us identically the same. This truth is more than intuitive; it is independent of our senses, of our imagination, of our memory, and of all our other relative faculties. The existence of our bodies, and of external objects, is however held in uncertainty by every unprejudiced reasoner; for what is that extension of length, breadth, and thickness, which we call our body, and which seems to be so much our own, but as it relates to our senses? What are even the material organs of those senses, but so many conformities with the objects that affect them? And with regard to our internal sense, has it any thing similar or in common with these external organs? Have the sensations excited by light or sound any resemblance to that tenuous matter, which seems to diffuse light, or to that tremulous undulation, which sound produces in the air? The effects are certainly produced by the necessary conformity there is between the eyes and ears, and those matters which act upon them. Is not that a sufficient proof, that the nature of the soul is different from that of matter? It is then a certain truth, that the internal sensation is altogether different from its cause; as also, if external objects exist, they are in themselves very different from what we conceive them. As sensation therefore bears no resemblance to the thing by which it is excited; does it not follow, that the causes of our sensations, necessarily differ from our ideas of them? The extension which we perceive by our eyes, the impenetrability, of which we receive an idea by the touch in all those qualities, whose various combinations constitute matter, are of a doubtful existence; since our internal sensations of extension, impenetrability, &c. are neither extended nor impenetrable, and have not even the smallest affinity with those qualities.