2002 Annual Science Report
University of Colorado, Boulder Reporting | JUL 2001 – JUN 2002
Philosophical Issues in Astrobiology
I finished the work that I had planned to do this year on issues concerning scientific methodology that pertain to astrobiological research. I applied the distinction (developed over the past two years) between the methodology of historical scientific research and experimental research to astrobiological research, discussing both the Viking lander experiments and the debate over whether ALH84001 contains fossilized Martian life (Cleland, Philosophy of Science, 2002, in press). Using the former as an example, I argue that the conditions for good experimental research cannot be met by in situ robotic experiments on other planets since the controls for the experiments must be designed in advance of the pertinent data; on the account of experimental science that I have developed (see Cleland, Geology, 2001, Philosophy of Science, 2002, in press), good experimental science requires that controlled experiments be designed in light of previous experimental results. I also argue (Philosophy of Science, 2002) that some of the controversy over ALH84001 derives from a misguided insistence that all research conform to experimental practice; I argue that the proper paradigm for research on the fossilized Martian life hypothesis is historical (vs. experimental) science.
I made good progress on the issue of whether life’ can be defined: The answer is no. The idea that a definition of life’ can be used to answer the question what is life? rests upon confusions about the nature of definition and its capacity to answer fundamental questions about natural categories. What is required to answer this question is a general theory of the nature of living systems. In the absence of such a theory, we are in the position analogous to that of a seventeenth century scientist trying to define water’ before the advent of molecular theory. The best she could have done would be to have defined it in terms of sensible properties such as being wet, transparent, odorless, tasteless, thirst quenching, and a good solvent. But no amount of observational or conceptual analysis of these features of water can reveal that water is H20. Yet this is the scientifically most informative answer to the question what is water?’ Analogously, in the absence of a general theory of the nature of living systems, analysis of the features that we currently associate with life is unlikely to provide a particularly informative answer to the question what is life?’ In collaboration with Christopher Chyba, this work has culminated in two articles (Cleland and Chyba, Orig. Life Evol. Biosph., 2002, in press; Cleland and Chyba, in Sullivan and Baross, eds., Ch. 7, forthcoming); Cleland and Chyba (in Sullivan and Baross, eds., Ch. 7, forthcoming) also explores some of the constraints that must be satisfied by an appropriately general theory of living systems and also talks about how to search for extraterrestrial life in the absence of either a definition of life’ or a general theory of living systems.