The answer is “yes” – to both. There are a finite set of ethical principles in the human world that almost all societies know – fairness, truth, duty, responsibility to others, compassion, etc. These are universal and unchanging.

Are ethics unchanging?

The answer would be yes. There are a limited set of ethical principles in the humanoid world that nearly all societies know - fairness, truth, duty, responsibility to others, compassion, etc. These are worldwide and unchanging.

How can we decide what kinds of performance enhancements are morally defensible?

We decide what kinds of performance enhancement are morally defensible by Moral Judgment. There are certainly ethical issues in our society in which we have to select an action but before we have to judge it whether its ethically right or wrong.