When we speak of the age that is passing, we shall have in mind what may roughly be reckoned as the last hundred years. That space includes, for those of us who are not in our first youth, the time of our {10} parents, and even, it may be, of our grandparents. The period has a certain distinctiveness of character in spite of superficial diversities. It was marked, as we have said, by the intelligence and vigour of its questionings. It was a time of intellectual movement and turmoil. It witnessed a succession of wonderful discoveries leading on to ever bolder investigations. Rapid generalisations were advanced, to be often as quickly abandoned. Only by degrees was it possible to see the new facts in their proper proportion and significance. Nor was it at all easy for men to keep their discussions free from heat and bitterness, when the most deeply-rooted convictions appeared to be assailed, and the most sacred associations to be regarded as of little account. Looking back, as we can, it is possible to see that in spite of the eddies and backwaters a steady progress was made. And it is of that progress that it will now be our endeavour to speak. We know how it has happened to us over and over again in our own individual experiences to have been made conscious of a gradual modification of our opinions as new evidence has reached us, and we have had time to relate it to our previous understanding and knowledge. We have had our first thoughts, and our second thoughts, and then there have come third thoughts, which were the ripest {11} and soundest of all. Just such a process of which we can mark the stages in ourselves is to be seen on a larger scale--in bigger print, as it were--in the thought movements of an age. In the case of the period which we are to review, the three stages have been more than commonly clear, as we shall aim to shew in the survey we are to make. We shall begin with the First thoughts, which were those of what may be termed the older orthodoxy. These were very generally accepted; indeed, they were regarded as for the most part beyond the reach of serious contradiction. Then we shall pass to the Second thoughts, which were forced upon an astonished and bewildered generation by the onslaughts upon traditional views that were made from the side of physical science. For fifty years or more the debate went on, with challenge and counter-challenge, and much noise and dust of controversy. They were great days, and in them great men fought with great courage in great issues. We shall seek to do justice to both sides, to those who dared to proclaim and suffer for the new, and to those who shewed an equal courage in their resolute determination to be loyal to what they held to be the truth of the old.