THOUGHTFUL men have long known that the campaign for the technological conquest of nature, conducted under the banner of modem science, would someday train its guns against the commanding officer, man himself. That day is fast approaching, if not already here. New biomedical technologies are challenging many of the formulations which have served since ancient times to define the specifically human—to demarcate human beings from the beasts on the one hand, and from the gods on the other. Birth and death, the boundaries of an individual human life, are already subject to considerable manipulation.  The perfection of organ transplantation and especially of mechanical organs will make possible wholesale reconstructions of the human body. Genetic engineering, a prospect already visible on the horizon, holds forth the promise of a refined control over human capacities and powers. Finally, technologies springing from the neurological and psychological sciences (e.g., electrical and chemical stimulation of the brain) will permit the manipulation and alteration of the higher human functions and activities—thought, speech, memory, choice, feeling, appetite, imagination, love.