In the past we could be resigned to the fact that our biology was going to drive us to do this no matter what. However, we are facing an era where we may be able to create sentient life synthetically. Either through artificial intelligence or by growing individuals en masse outside the womb.
The excuse – my biological clock made me do it – will no longer cut it and we may be talking about trillions of lives here. If we get this wrong it will be the greatest moral crime ever committed.
In this model of the world there is only resources, and they are directly consumed. Imagine, for instance, if your two people with two living children have a third child whose inventions increase the efficiency of solar power by 1%, or increases grain yields, or leads to a new low cost recycling technique. This person coming into existence has clearly increased the amount of output than can be created with the resources on earth. The way Population Matters has formulated the problem of scarcity only makes sense if… well, if you’re determined for some reason to try and argue that more population is a really bad thing.
My comment to Ozimek is a rehash of my questions for Bryan Caplan:
Both you and Bryan Caplan seem willing to trade off very uncertain, speculative, indirect effects (inventions, etc.) of population against the direct, quite certain physical effects. Why do speculative positive effects matter more than definite negative effects? Or do you think the negative effects are somehow themselves speculative? Is the reality of scarcity of important stuff really in question?
Also, your connection between having the third child and inventions seems to imply causation from population to nice inventions (which Caplan also assumes). What evidence supports the theory that population drives innovation in a significant, reliable way? It seems the global distribution of both innovation and population would call that relationship into doubt...Just looking at the distribution of patents or Nobel prizes, it seems there are dozens of variables that correlate better with these than population. Are you talking U.S. only, or is this also supposed to apply to Brazil and China and Kenya and India and Israel equally?