Searching for extraterrestrial life without a definition of life

Carol Cleland will be speaking with us about searching for life without (being able to? having to?) define life. Carol is Professor of Philosophy at University of Colorado, a member of Colorado University’s Center for Astrobiology, Director of the Center for Study of Origins, and author of the recent book "The Quest for a Universal Theory of Life: Searching for Life As We Don't Know It". The title and abstract of her talk, and some useful references to read in preparation, are below. 

Title: Searching for extraterrestrial life without a definition of life

Abstract: It is often claimed that astrobiologists need a definition of life to search for extraterrestrial life: How else can one recognize alien life if one is fortunate enough to encounter it? This talk begins by briefly explaining why definitional approaches to defining life are badly mistaken, reflecting misunderstandings about the nature of definitions, their capacities to answer questions about natural categories, and their relationship to scientific theories. I propose an alternative strategy for searching for extraterrestrial life:  Search for potentially biological anomalies (as opposed to life per se) using tentative (vs. defining) criteria.  The function of tentative criteria is not, like that of defining criteria, to decide the question of life.  Instead, it is to identify phenomena that are especially difficult to classify as living or nonliving as worthy of further scientific investigation for the possibility of novel life. While the proposed strategy resembles that of current life-detection missions, insofar as it advocates the use of a variety of lines of evidence (including "agnostic biosignatures"), it differs from these approaches in ways that increase the likelihood of noticing truly novel forms of life, as opposed to dismissing them as just another poorly understood abiotic phenomenon. Finally, the strategy under consideration would be just as effective at detecting forms of life closely resembling our own as a definition of life.

References:

Cleland, C.E. (2019). The Quest for a Universal Theory of life: Searching for life as we don't know it,  Cambridge: Cambridge University Press, Ch. 8.

Cleland, C.E.  (2019).  "Moving beyond Definitions of Life in the Search for Extraterrestrial Life", Astrobiology 9, pp. 722-729.