2003 Annual Science Report
University of Colorado, Boulder Reporting | JUL 2002 – JUN 2003
Philosophical Issues in Astrobiology
I have continued my work on the issue of defining 'life’. Detailed studies of the history of other scientific discoveries (e.g., the chemical composition of water, 17th century debate over whether bats are birds) reveal that defining a natural kind term (a term that designates a category of nature that is independent of human interests and concerns) in the absence of an adequately general theory does not advance scientific understanding of the phenomenon concerned and indeed may even retard the development of an adequately general theory of the phenomena. In short, logical and historical considerations demonstrate that it is a mistake to try to define 'life’ in the absence of an adequately general theory of life.
I have also begun investigating the issue of how one can search for extraterrestrial life in the absence of a definition of 'life’ or a general theory of living systems. The key is to have a set of reliable biosignatures for detecting terrestrial life and to use them not as definitive (as necessary and/or sufficient conditions) for life but as grounds for suspicion that life is or has been present; it is important that they not be considered definitive because there is no way of knowing in advance which ones are universal to life and which ones are unique to the peculiar circumstances (e.g., primordial conditions on the primitive Earth, contingencies of evolution) of life on Earth. This research is bringing together my earlier work on the methodology of historical science since the search for biosignatures is primarily a search for traces of past life. I am optimistic that this work will eventually yield a more effective strategy for searching for extraterrestrial life than the ones currently being employed by NASA.