Ingmar Persson and Julian Savulescu1 warn of our destruction by the cognitively enhanced beings we create. Now, in a fascinating paper, Nicholas Agar2 warns of an even more disturbing prospect: cognitively enhanced beings may be entitled to sacrifice us for their own ends. These post-humans would likely conclude that they had higher moral status than we mere human beings, and we would have good reason to defer to their vastly superior moral knowledge. We would lack even the consolation of moral complaint.

I will question both these claims: that we would have good reason to accept the conclusion of cognitively enhanced beings that they had superior moral status, and that they would be likely to reach such a conclusion (in good faith). I will also question whether, if they were to have higher moral status, it would be wrong to create them, because it would be wrong to create beings with such costly needs.

Agar argues that moral truths, including those about moral status, are like mathematical truths in eventually yielding to expert reasoning. This belief in moral enlightenment is extreme even for a moral realist. Michael Smith,3 whom Agar cites, merely adduces the gradual consensus that has emerged about issues that were once the subject of seemingly intractable disagreement: slavery, workers’ and women's rights and democracy. One may agree with Smith about slow, halting, moral progress, …