Abstract In an intriguing essay, G. A. Cohen has defended a conservative bias in favour of existing value. In this paper, we consider whether Cohen’s conservatism raises a new challenge to the use of human enhancement technologies. We develop some of Cohen’s suggestive remarks into a new line of argument against human enhancement that, we believe, is in several ways superior to existing objections. However, we shall argue that on closer inspection, Cohen’s conservatism fails to offer grounds for a strong sweeping objection to enhancement, and may even offer positive support for forms of enhancement that preserve valuable features of human beings. Nevertheless, we concede that Cohen’s arguments may suggest some plausible and important constr...