In 1779, the French Academy of Science offered a prize of one kilo of gold to anyone who could explain the nature of alcohol fermentation. For 6000 y, fermentation had been regarded as a mysterious power of transformation, a meeting of the material and the spiritual. But now, in the age of science, a bitter dispute arose between those representing the new field of chemistry and the traditional "vitalists," who maintained that life processes are not reducible to explanations in terms of physio-chemical mechanism (1).
Toward the end of the 18th century, Lavoisier had noted that the powers of fermentation could be transferred with residual sediments. By the middle of the 19th century, Schwann established that cells are the basic unit of life, and that yeast cells could be found in fermentation sediments. The crucial role of these yeast cells was confirmed by Pasteur, who maintained that only within the living system of the cell, with its mysterious, immaterial vital forces, could the powers of fermentation be manifest. But in 1897, the German chemist Eduard Büchner prepared an extract of yeast and noted that this clear, slightly yellow, filtered fluid was fully capable of fermentation even apart from its cellular source.
Büchner's discovery led to the isolation of the enzymes of fermentation and the chemical description of this fundamental organic process. With this decisive blow to vitalism, the field of biochemistry was born and with it the reductive and analytic approach to the study of life.
The practical significance of this conceptual revision is evident in the dramatic advances in biology throughout the 20th century. By breaking down organic systems into their component parts and looking at living beings in terms of inanimate matter, we opened an era of scientific discovery that has culminated in the sequencing of the human genome. Now, however, as we move from genomics to proteomics and on to the investigation of developmental biology, we are returning to the study of whole living beings. When applied to human biology, this inquiry reopens the most fundamental questions concerning the very definition of life and the adequacy of our current scientific approach to inform discussion of the ethical dilemmas raised by our new perspectives and powers.
These questions have been forced to the foreground of public awareness by our deepening controversy over embryonic stem cell (ESC) research, and most specifically by proposals for the production of cloned human embryos as a source of these cells. This conflict is sometimes framed as a battle between the subjectivity of personal religious belief and the objectivity of science, but it is far more fundamental than that. Distilled in this difficult debate are the most profound considerations concerning the relationship between the material, physiochemical mechanisms and the moral meaning of human life.
A careful consideration of the foundations of this controversy can place it within a broader social and scientific context and bring into focus the crucial concerns that underlie our present political impasse. Drawing on this debate, particularly as it developed within the President's Council on Bioethics (on which I serve), we can discuss the immediate ethical issues in ESC research. At the same time, we can seek a wider understanding that may set the frame for scientific and medical advance in the era of developmental biology. It is clear that ESC research is just the first of many dilemmas that will challenge our traditional understanding of human life. Parthenogenesis, human-animal chimeras, human body parts grown in laboratories—these and a wide range of other emerging technologies make it imperative that we define the boundaries of humanity with clarity and precision to preserve the essential unity of the human person.
Through such a reflection on the meaning of human embodiment, we may draw a distinction between the material parts and the living whole that defines the locus of our moral concern. This distinction may suggest a way forward that will allow positive progress in biomedical science while preserving our most fundamental principles for the protection of human subjects and the defense of human dignity.