The purpose of this paper is to evaluate the plausibility of the claim that the alteration of human nature through cutting-edge technology will result in the desecrating moral values including human dignity. For this, I first clarify the meanings of human nature and then inquire how human nature is related to the realm of ethical values including human dignity. I distinguishes 3 different ways in which human nature can be involved in the ethical discourses. Human nature can be thought of as conditions of practical rationality and moral agency (HN1), as a feasibility constraint on morality (HN2), and as a constraint on the good for humans (HN3). I argue that there are partially good reasons to object to human enhancement that are deducible from each of (HN1)-(HN3). However, none of them can offer a sufficiently good reason to object to human enhancement in general.