To examine the moral implications of human enhancement, we first require a definition of what it is to enhance a human being. We present a conceptual pluralism that acknowledges two ways to define human enhancement. These concepts highlight different moral problems and opportunities that emerge from the application of powerful genetic and environmental technologies to human beings. Distinct moral issues arise in respect of different means, degrees, and targets of enhancement. We begin by describing various means by which humans may be enhanced. Philosophical interest in human enhancement has tended to focus on enhancement by the modification or selection of human genetic material. This focus risks overlooking a variety of other ways in which humans may be enhanced. Enhancement can also occur through environmental means. Cochlear implants, electronic hippocampi, prosthetic legs, and traditional methods of education all involve the modification of human brains or bodies, and thus are all examples of environmental enhancements.