There is the same sort of continuity and unity in thought The preoccupations of man are the same in all ages--to provide for his material needs, and to speculate what can possibly happen to his spirit, when the body, broken by accident or disease or decay, can no longer contain his soul. The best thought of man has always been centred on trying to devise some sort of future hope which could encourage him to live eagerly, to endure patiently, to act rightly. As science opens her vast volume before us, we naturally become more and more impatient of the hasty guesses of man, in religion and philosophy, to define what we cannot yet know; but we ought to be very tender of the old passionate beliefs, the intense desire to credit noble and lofty spirits, such as Buddha and Mahomet, with some source of divinely given knowledge. Yet of course there is an inevitable sadness when we find the old certainties dissolving in mist; and we must be very careful to substitute for them, if they slip from our grasp, some sort of principle which will give us freshness and courage. To me, I confess, the tiny certainties of science are far more inspiring than the most ardent reveries of imaginative men. The knowledge that there is in the world an inflexible order, and that we shall see what we shall see, and not what we would like to believe, is infinitely refreshing and sustaining. I feel that I am journeying onwards into what is unknown to me, but into something which is inevitably there, and not to be altered by my own hopes and fancies. It is like taking a voyage, the pleasure of which is that the sights in store are unexpected and novel; for a voyage would be a very poor thing if we knew exactly what lay ahead, and poorer still if we could determine beforehand what we meant to see, and could only behold the pictures of our own imaginations. That is the charm and the use of experience, that it is not at all what we expect or hope. It is in some ways sadder and darker; but it is in most ways far more rich and wonderful and radiant than we had dreamed. What I grow impatient of are the censures of rigid people, who desire to limit the hopes and possibilities of others by the little foot-rule which they have made for themselves. That is a very petty and even a very wicked thing to do, that old persecuting instinct which says, "I will make it as unpleasant for you as I can, if you will not consent at all events to pretend to believe what I think it right to believe." A man of science does not want to persecute a child who says petulantly that he will not believe the law of gravity. He merely smiles and goes on his way. The law of gravity can look after itself! Persecution is as often as not an attempt to reassure oneself about one's own beliefs; it is not a sign of an untroubled faith.