And, as man is unequal to himself, so is man to his neighbour, and period to period. The entire method of action, the theories of human life which in one era prevail universally, to the next are unpractical and insane, as those of this next would have seemed mere baseness to the first, if the first could have anticipated them. One epoch, we may suppose, holds some 'greatest nobleness principle,' the other some 'greatest happiness principle;' and then their very systems of axioms will contradict one another; their general conceptions and their detailed interpretations, their rules, judgments, opinions, practices will be in perpetual and endless collision. Our minds take shape from our hearts, and the facts of moral experience do not teach their own meaning, but submit to many readings according to the power of the eye which we bring with us. The want of a clear perception of so important a feature about us leads to many singular contradictions. A believer in popular Protestantism, who is also a believer in progress, ought, if he were consistent, to regard mankind as growing every day towards a more and more advantageous position with respect to the trials of life; and yet if he were asked whether it was easier for him to 'save his soul' in the nineteenth century than it would have been in the first or second, or whether the said soul was necessarily better worth saving, he would be perplexed for an answer. There is hardly one of us who, in childhood, has not felt like the Jews to whom Christ spoke, that if he had 'lived in the days of the Fathers,' if he had had their advantages, he would have found duty a much easier matter; and some of us in mature life have felt that in old Athens, or old republican Rome, in the first ages of Christianity, in the Crusades or at the Reformation, there was a contagious atmosphere of heroism, in which we should have been less troubled with the little feelings which cling about us now. At any rate, it is at these rare epochs only that real additions are made to our moral knowledge. At such times, new truths are, indeed, sent down among us, and, for periods longer or shorter, may be seen to exercise an elevating influence on mankind. Perhaps what is gained on these occasions is never entirely lost. The historical monuments of their effects are at least indestructible; and when the spirit which gave them birth reappears, their dormant energy awakens again.