It is natural that we, who are such self-centered beings, should want to live for ever, either here or in some heaven. It is natural that we should demand some kind of immortality for those whom we love and admire. But, as I see it, not only must these cravings remain unfulfilled, but also it is better so. I must learn to regard myself and every other individual, even my dearest, as having the kind of excellence that a theme or phrase of music has. The phrase must not go on all through the music. It has its proper place. It must come to an end, and make way for other musical forms. So also with the man and woman.

Even the lengthening of the life-span would raise a serious population problem. Obviously, if all men and women are to last for many thousands of years, reproduction must be greatly reduced. It must therefore be regarded as a very rare and noble privilege. And those to whom it is not permitted must turn their energies in other directions. We are sometimes told that parenthood is a function without which the human spirit cannot flourish. I do not believe it; but if so, then here is another respect in which we must change human nature. A function which was very important in early days may well have to be restricted before man can become mature.

What other alterations can we imagine?

Perhaps it will be possible some day to increase man's sensory powers. Sight, for instance, cries out for improvement. Future man might see ultra-violet and infra-red colours. And he might analyse our present primary colours into several new ones. Moreover, by equipping his eyes with many more of the microscopic units of sight, he might become capable of much more detailed seeing. Thus, to take an unimportant example, when flying at a great height over a city, he would be able to single out, from the crowd of upturned faces, the men and the women, the young and the old, the blue eyes and the brown, and his own particular acquaintances. Similar improvements might be devised for the other senses. Perhaps entirely new senses might be created, such as a direct awareness of minute electrical changes.

Memory, also, might be so perfected that the individual's whole past might be recalled at will in all its original detail and vividness.

There might also be great improvements in man's perception of time in two manners. In the first place, he may come to hold together a longer span of time in one "now." Thus he might perceive in one act of vision the longer rhythms of nature, such as day and night, or even the four seasons, as we perceive the movements of dancing or a stroke in tennis. Yet also, perhaps, his perception might be so refined that when a musical tune was sounded, he might at will either hear it as a single quality or sound, or distinguish its separate pulsations, as we do the ticks of a clock.

Great improvements will probably occur in man's intelligence. I myself, who am perhaps not much below average intelligence, find much difficulty in coping with my own unimposing income tax returns. Imagine a man of the far future entering our present world and discovering our social and economic confusion. He would see the solution of it all in a flash, just as we solve those little problems that small children bring us, with tears of despair. "Why," he would say, "this is what you must do, and this." And (still greater miracle) he would probably have such powers of persuasion that he would actually get us to do the sensible thing. Imagine him also talking to our scientists and philosophers. "My dear fellows," he would say, "your theories are unnecessarily cumbersome and fantastic. Try this new starting point, and all will be clear." And then (greatest miracle of all) he would get them to share some fraction of his own insight.

By far the most important improvements in man I have still to mention.