This article addresses the slippery slope argument in ethics and bioethics, and demonstrates that a lack of consensus about human nature and what constitutes a person contributes to its frequent use in such areas. Rationality and autonomy are contrasted with sentence, and a utilitarian quality of life approach with a deontological sanctity of life approach as defining criteria of personhood. It is argued that the concept 'quality of life' is itself a slippery slope. Genetic engineering is discussed as a paradigm of the slippery slope argument in use, as well as IVF, and the distinction between experimental and therapeutic research-both issues of concern to feminists. Australia has been a leader of scientific research in the new reproductive technologies, with regulative thinking following the technological breakthroughs. The question is posed whether biotechnology will repeat a similar pattern.