Hope . . . means . . . a continual looking forward to the eternal world. . . . It does not mean that we are to leave the present world as it is.
If you read history you will find that the Christians who did most for the present world were just those who thought most of the next. . . . It is since Christians have largely ceased to think of the other world that they have become so ineffective in this.
Aim at Heaven and you will get earth “thrown in”: aim at earth and you will get neither.
Forget that old cliché about being too heavenly minded to be of much earthly good. Lewis is correct when he says the only way we’ll be of any earthly good is to have heaven on our minds.