Lastly, there is a fourth class of people who take whatever it is that they happen to want, and say that that is the ultimate aim of evolution. And these are the only sensible people. This is the only really healthy way with the word evolution, to work for what you want, and to call that evolution. The only intelligible sense that progress or advance can have among men, is that we have a definite vision, and that we wish to make the whole world like that vision. If you like to put it so, the essence of the doctrine is that what we have around us is the mere method and preparation for something that we have to create. This is not a world, but rather the materials for a world. God has given us not so much the colours of a picture as the colours of a palette. But He has also given us a subject, a model, a fixed vision. We must be clear about what we want to paint. This adds a further principle to our previous list of principles. We have said we must be fond of this world, even in order to change it. We now add that we must be fond of another world (real or imaginary) in order to have something to change it to.