I have previously reduced the whole science of logic to two facts.The first is that our perceptions being every thing for us, we areperfectly, completely, and necessarily sure of whatever we actually feel.The second is that consequently none of our judgments, separatelytaken, can be erroneous: inasmuch as we see one idea in another it isactually there; but their falsity, when it takes place, is purely relativeto anterior judgments, which we permit to subsist; and it consists inthis, that we believe the idea in which we perceive a new element tobe the same as that we have always had under the same sign, when itis really different, since the new element which we actually see thereis incompatible with some of those which we have previously seen;so that to avoid contradiction we must either take away the former ornot admit the latter.