Nicholas Agar argues that it is possible, and even likely, that radically enhanced human beings will turn out to be ‘post-persons’, that is, beings with a moral status higher than that of mere persons such as us.1 This would mean that they will be morally justified in sacrificing our lives and well-being not merely in cases of emergency, but also in cases of ‘supreme opportunities’ (of which there will be many), that is, whenever such a sacrifice leads to ‘significant benefits for post-persons’. For this reason, Agar believes, it would be morally wrong to allow any cognitive enhancement of people that might entail the risk of moral status enhancement.

However, neither are there sufficient grounds to expect radically enhanced human beings to have a higher moral status than unenhanced human beings, nor would it, even if they did, be morally wrong to bring about their existence. We use moral status ascriptions mostly as a convenient shorthand to indicate a difference in capacities that strikes us as morally relevant. Rocks have zero moral status because they cannot feel or think, so we cannot hurt or kill them. Whatever we do to them, it does not affect them. Animals, on the other hand, …