This chapter attacks various philosophical doctrines, remarkably popular nowadays, which cast doubt on any real ethical need to keep the human race in existence. (1) Many philosophers think it quaintly out of date to believe that ethical needs, ethical requirements, are ‘elements of reality’ like geographical or mathematical facts. They interpret all talk of such needs as mere expressions of emotion; or they say that calling acts of certain types ‘ethically needful’ is just prescribing that everyone is to perform such acts; and so on. (2) Other philosophers have doubted whether the human race should be encouraged to survive if even a small proportion of lives were unhappy. (3) Again, there are those who suggest that duties are always towards people who now exist, or whose existence is more or less inevitable. There can therefore be little call to bring happy people into being unless already existing folk happen to want it.
In view of all the threats confronting the human race, very vigorous efforts could well be needed if it is to survive long. Can we tell people that they truly ought to make these efforts? That this is quite as much a matter of what really is so as the fact that three fives make fifteen?