It must be recollected that certitude is a deliberate assent given expressly after reasoning. If then my certitude is unfounded, it is the reasoning that is in fault, not my assent to it. It is the law of my mind to seal up the conclusions to which ratiocination has brought me, by that formal assent which I have called a certitude. I could indeed have withheld my assent, but I should have acted against my nature, had I done so when there was what I considered a proof; and I did only what was fitting, what was incumbent on me, upon those existing conditions, in giving it. This is the process by which knowledge accumulates and is stored up both in the individual and in the world. It has sometimes been remarked, when men have boasted of the knowledge of modern times, that no wonder we see more than the ancients, because we are mounted upon their shoulders. The conclusions of one generation are the truths of the next. We are able, it is our duty, deliberately to take things for granted which our forefathers had a duty to doubt about; and unless we summarily put down disputation on points which have been already proved and ruled, we shall waste our time, and make no advances. Circumstances indeed may arise, when a question may legitimately be revived, which has already been definitely determined; but a re-consideration of such a question need not abruptly unsettle the existing certitude of those who engage in it, or throw them into a scepticism about things in general, even though eventually they find they have been wrong in a particular matter. It would have been absurd to prohibit the controversy which has lately been held concerning the obligations of Newton to Pascal; and supposing it had issued in their being established, the partisans of Newton would not have thought it necessary to renounce their certitude of the law of gravitation itself, on the ground that they had been mistaken in their certitude that Newton discovered it.