Carol Cleland

University of Colorado, Boulder, Philosophy, Faculty Member

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I am a philosopher with an extensive interest and background in natural science. I have a B.A. in mathematics from the University of California (Santa Barbara) and a Ph.D. in philosophy from Brown University. My current position is Full Professor of Philosophy at the University of Colorado (Boulder). Before I became a philosopher, I was a software engineer. After receiving my Ph.D. in philosophy, I spent a year on a postdoctoral fellowship in philosophy and computer science at Stanford University’s Center for the Study of Language and Information (CSLI). I am affiliated with the NASA Astrobiology Institute (NAI) and a Co-I in the Center for Astrobiology at the University of Colorado and Director of the University of Colorado’s new Center for the Study of Origins.

My research is focused in the areas of philosophy of science, philosophy of logic and metaphysics. I am particularly interested in the methodology and justification of historical science, the nature of scientific theories and the role of models in science, philosophy of biology (microbiology, astrobiology, the origins of life, the nature of life, and the possibility of a ‘shadow biosphere’, a term which I coined), the limits to physical computability (especially the history and justification of the Church-Turing thesis), and the nature of causation (including issues about mechanism and emergence).

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Papers by Carol Cleland

Ammonia and Phosphine in the Clouds of Venus as Potentially Biological Anomalies

Aerospace

We are of the opinion that several anomalies in the atmosphere of Venus provide evidence of yet-u... more We are of the opinion that several anomalies in the atmosphere of Venus provide evidence of yet-unknown processes and systems that are out of equilibrium. The investigation of these anomalies on Venus should be open to a wide range of explanations, including unknown biological activity. We provide an overview of two anomalies, the tentative detection of ammonia and phosphine in Venus’s atmosphere. These anomalies fly in the face of the tacit assumption that the atmosphere of Venus must be in chemical redox equilibrium, an assumption connected to the belief that Venus is lifeless. We then discuss several major past discoveries in astronomy, biology and geology, which lead to the abandonment of certain assumptions held by many scientists as though they were well-established principles. The anomalies of ammonia and phosphine in the atmosphere of Venus are placed in the context of these historical discoveries. This context supports our opinion that persistence by the community in the ex...

format_quotePrevious probes observed phenomena in Venus' atmosphere conflicting with the assumption of chemical redox equilibrium.format_quote

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Why astrobiologists should NOT get rid of the term ‘life’

Primordial Scoop

Cleland and Grinspoon response to Benner: Do synthetic microbes provide another example of life?

Primordial Scoop

The Problem with Agnostic Biosignatures

Primordial Scoop

Why the term ‘life’ is important to research in astrobiology

Primordial Scoop

Thoughts on Benner’s “Life, the Universe, and the Scientific Method”

Primordial Scoop

Why searching for extraterrestrial life with a universal biosignature detection framework is a mistake

Primordial Scoop

The Quest for a Universal Theory of Life

Hidden Concepts in the History and Philosophy of Origins-of-Life Studies: a Workshop Report

Origins of Life and Evolution of Biospheres, 2019

In this review, we describe some of the central philosophical issues facing origins-of-life resea... more In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we provide brief summaries of debates with respect to (1) definitions (or theories) of life, what life is and how research should be conducted in the absence of an accepted theory of life, (2) the distinctions between synthetic, historical, and universal projects in origins-of-life studies, issues with strategies for inferring the origins of life, such as (3) the nature of the first living entities (the "bottom up" approach) and ( ) how to infer the nature of the last universal common ancestor (the "top down" approach), and (5) the status of origins of life as a science. Each of these debates influences the others. Although there are clusters of researchers that agree on some answers to these issues, each of these debates is still open. With respect to history, we outline several independent paths that have led to some of the approaches now prevalent in origins-of-life studies. These include one path from early views of life through the scientific revolutions brought about by Linnaeus (von Linn.), Wöhler, Miller, and others. In this approach, new theories, tools, and evidence guide new thoughts about the nature of life and its origin. We also describe another family of paths motivated by a" circularity" approach to life, which is guided by such thinkers as Maturana & Varela, Gánti, Rosen, and others. These views echo ideas developed by Kant and Aristotle, though they do so using modern science in ways that produce exciting avenues of investigation. By exploring the history of these ideas, we can see how many of the issues that currently interest us have been guided by the contexts in which the ideas were developed. The disciplinary backgrounds of each of these scholars has influenced the questions they sought to answer, the experiments they envisioned, and the kinds of data they collected. We conclude by encouraging scientists and scholars in the humanities and social sciences to explore ways in which they can interact to provide a deeper understanding of the conceptual assumptions, structure, and history of origins-of-life research. This may be useful to help frame future research agendas and bring awareness to the multifaceted issues facing this challenging scientific question.

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Science and the Messy, Uncontrollable World of Nature

Reconsidering the Demarcation Problem

Understanding the Nature of Life: A Matter of Definition of Theory?

Philosophical Issues in Natural History and Its Historiography

Tucker/A Companion to the Philosophy of History and Historiography, 2009

Is a General Theory of Life Possible? Seeking the Nature of Life in the Context of a Single Example

Biological Theory, 2012

Is one of the roles of theory in biology answering the question ''What is life?'' This is true of... more Is one of the roles of theory in biology answering the question ''What is life?'' This is true of theory in many other fields of science. So why should not it be the case for biology? Yet efforts to identify unifying concepts and principles of life have been disappointing, leading some (pluralists) to conclude that life is not a natural kind. In this essay I argue that such judgments are premature. Life as we know it on Earth today represents a single example and moreover there is positive evidence that it may be unrepresentative of life considered generally. Furthermore, as I discuss, the prototype for theorizing about life has traditionally been based on multicellular plants and animals. Yet biologists have discovered that the latter represent a rare, exotic, and fairly recent form of Earth life. By far the oldest, toughest, most extensive, and diverse form of life on our planet is unicellular, prokaryotic microbes, and there are reasons to suppose that this is almost certainly true elsewhere in the universe as well. If there are explanatorily and predictively powerful, biologically distinctive principles for life that can be gleaned from our insular example of life it is more likely that they will be found among the microbes. I discuss some provocative ways in which unicellular microbes differ from multicellular eukaryotes and argue that some of them just might provide us with key insights into the nature of life.

format_quoteThe N = 1 problem suggests familiar Earth life is unrepresentative, complicating formulation of a universal theory of life.format_quote

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Common cause explanation and the search for a smoking gun

Rethinking the Fabric of Geology, 2013

The hypotheses of historical natural science are typically concerned with long past, singular eve... more The hypotheses of historical natural science are typically concerned with long past, singular events and processes, e.g., what caused the end-Cretaceous mass extinction. Evidence for such occurrences is acquired through fi eld studies in the messy, uncontrollable world of nature. Because hypotheses about the remote past cannot be directly tested in the classical manner of experimental science, historical science is sometimes judged inferior. Building on earlier work, this essay explains the motivation for such arguments and why they are fundamentally mistaken. Traditional versions of the scientifi c method (inductivism and falsifi cationism) are based upon a deeply fl awed, one-size-fi ts-all, logical analysis of the evaluative relation between hypothesis and observation. The distinctive methodologies of historical and experimental science, however, refl ect pervasive causal differences in their evidential situations. The evidential reasoning of historical scientists is founded upon the principle of the common cause, which asserts that seemingly improbable associations among present-day traces of the past are best explained in terms of a common cause. The truth of the principle of the common cause rests upon a physically pervasive, time asymmetry of causation: In a nutshell, the present contains records of the past but not of the future. Viewed in this light historical scientists actually have an evidential advantage over classical experimentalists.

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What Is Life?