New realities and old classifications: a problem in medical ethics.

Advances in research and technology are forcing us to confront hitherto unknown forms of life on both macroscopic and microscopic levels. Genetically engineered cells, human embryos growing in Petri dishes or preserved in freezers, human beings without hearts or functioning brains, these are just a few examples of the new forms of life. The challenge now is to determine what actions relative to these unfamiliar realities are morally acceptable.