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Counterfactual Thinking in Biology




PI: Prof. Dr. Marcel Weber, Department of Philosophy, Université de Genève

Ph.D. Students: Maximilian Huber, M.Litt; Guillaume Schlaepfer, M.A.


Counterfactual thinking plays an important role in the biological sciences and manifests itself in various forms and contexts. First, like other sciences, biology produces causal statements that, according to received accounts of causation, imply counterfactual conditionals (and perhaps are implied by such conditionals, although this is more controversial). Second, biological science establishes causal regularities that may vary with respect to their stability or invariance. Such differences, too, can be analyzed in terms of certain patterns of counterfactual dependence (Woodward 2003). Third, there exist general claims about the biological claim that are counterfactual in nature. An example is Stephen Jay Gould's claim that evolution is like a tape that would play a different tune every time it is replayed (Gould 1989). Fourth, biological explanation often refer to possible organisms in addition to actual organisms. For example, in functional explanations or design explanations, actual organisms are compared to possible but non-actual organisms that are identical to the actual ones in all respects but the trait to be explained functionally or in terms of design (Wouters 2003; Knell and Weber 2009, section 2.5.2). Some such explanations also contain constraints arising fron the living state (Wouters 2007). Fifth, counterfactual claims are not only made about organisms but about biology itself. An example are claims of the historical contingency of the development of science (Radick 2006; Weber 2005, Ch. 6). In other words, biologists made have accepted other theories than they actually did had the historical conditions been different.

In the research group, biology is taken to be a representative for the natural sciences that takes an intermediate between fundamental physics and the humanities (P4, P5). Based on a theory of biological modality, we want to establish a framework for analyzing and reconstructing various instances of counterfactual thinking in biology.

To date, there have hardly been any attempts of giving a systematic account of the truth conditions as well as the epistemic warrants for claims about biological modalities (i.e, biological possibility and necessity). No doubt, the vast existing literature on biological laws and causal regularities (e.g., Beatty 1995; Cooper 1996; Waters 1998, 2007; Weber 1999; Mitchell 2000; Woodward 2010) is relevant to this topic. Just as physical modalities can be analyzed in terms of possible worlds in which certain laws obtain, we might attempt to understand biological modalities in terms of biological laws. However, in contrast to physics, it is often not clear which laws or regularities might be relevant for the task. This is precisely why biological modalities merit philosophical scrutiny in their own right. It is possible that biological modalities are more fundamental than any biological laws or causal regularities. An indication of this fact is that current accounts of biological regularities deploy counterfactual conditionals (P1, P2) the truth- or assertability conditions of which are unknown. Such conditionals express modalities that we do not presently understand with respect to their ontological grounds nor what warrants such claims epistemically. This project aims to remedy this unsatisfactory state of affairs. It contains two parts, where Part 1 deals with ontological and part 2 with epistemological questions.


Part 1: Biological Possibility and Necessity

Modal claims, i.e., claims about what is and what is not possible or necessary are frequently encountered in biology, just as in other sciences. However, some claims do not fit the standard distinctions, for example, the distinction between logical and physical possibility. Some state of affairs are said to be biologically impossible without implying physical impossibility (while the converse is always thought to be true: physical impossibility entails biological impossibility). For example, a complex organism that shows no senescence (aging) is thought to be physically possible but biologically impossible (Knell and Weber 2009, Ch. 2). Other examples of specifically biological modal claims are found in evolutionary developmental biology ("evo-devo"), where the notion of developmental contraint is frequently encountered (Amundsen 2005). Developmental constraints are trait combinations that are not changeable through evolution, but the reason is not that such forms would be physically impossible. The notion of developmental constraint contains only biological impossibility, not physical impossibility.

This part of the project will analyze various forms of modal claims in biology and examine different attempts of stating the truth (or assertability) conditions for those counterfactual conditionals (P1, P2) that are normally used to express such modal facts.


Part 2: Thought Experiments in Biology

In contrast to real experiments (Weber 2005), biological thought experiments have not received much attention. To date, most discussion centered around Dennett's (1994) suggestions, according to which the approach known as Artificial Life (AL) is best viewed in terms of thought experiments (Swan 2009). Although AL is not taken very seriously in general, there might be areas within biology that may also be viewed in such terms, for example, so called in silico-experiments, which play an increasingly important role in the field of systems biology. In addition, there are historical examples of biological thought experiments, for example, R.A. Fisher's three sex-reproduction (Fisher 1930). Just as in other areas where thought experiments are used (P3, P6), the question is of there is some kind of a priori-knowledge in science or of thought experiments play some other role that conforms with an empiricist philosophy of science (Sorensen 1992; Brown 2004; Norton 2004).

Like projects P3, P4 and P6, this part of the project examines how thought experiments can function as epistemic tools for the establishment of modal claims (see Part 1). It is also planned to examine the considerable literature on modeling in general philosophy of science (e.g., Morrison 1999).



Amundson, Ronald (2005), The Changing Role of the Embryo in Evolutionary Biology : Roots of Evo- devo. Cambridge: Cambridge University Press.

Beatty, John (1995), "The Evolutionary Contingency Thesis", in Gereon Wolters, James G. Lennox and Peter McLaughlin (eds.), Concepts, Theories, and Rationality in the Biological Sciences. The Second Pittsburgh-Konstanz Colloquium in the Philosophy of Science, Konstanz/Pittsburgh: Universitätsverlag Konstanz/University of Pittsburgh Press, 45–81.

Brown, James Robert (2004), "Why Thought Experiments Transcend Empiricism", in Christopher Hitchcock (ed.), Contemporary Debates in Philosophy of Science, Oxford: Blackwell, 23–43.

Cooper, Gregory (1996), "Theoretical Modelling and Biological Laws", Philosophy of Science 63 (Proceedings), 28–35.

Dennett, Daniel (1994), "Artificial Life as Philosophy", in Artificial Life 1, 291–292.

Fisher, R. A. (1930), The Genetical Theory of Natural Selection. Oxford: Clarendon.

Gould, S. J. (1989), Wonderful Life: The Burgess Shale and the Nature of History. London: Hutchinson Radius.

Knell, Sebastian and Marcel Weber (2009), Menschliches Leben. Berlin: Walter de Gruyter.

Mitchell, Sandra (2000), "Dimensions of Scientific Law", in Philosophy of Science 67, 242–265.

Morrison, Margaret (1999), Models as Mediators. Perspectives on Natural and Social Science. Cambridge: Cambridge University Press.

Norton, John D. (2004), "Why Thought Experiments Do Not Transcend Empiricism", in Christopher Hitchcock (ed.), Contemporary Debates in Philosophy of Science, Oxford: Blackwell, 44–66.

Radick, Gregory (2005), "Other Histories, Other Biologies", in Anthony O'Hear (ed.), Philosophy, Biology and Life, Cambridge: Cambridge University Press, 21–47.

Sorensen, Roy A. (1992), Thought Experiments. Oxford: Oxford University Press.

Swan, Liz Stillwaggon (2009), "Synthesizing Insight: Artificial Life as Thought Experimentation in Biology", in Biology and Philosophy 24 (4), 687–701.

Waters, C. Kenneth (1998), "Causal Regularities in the Biological World of Contingent Distributions", in Biology and Philosophy 13, 5–36.

Waters, C. Kenneth (2007), "Causes That Make a Difference", in The Journal of Philosophy CIV, 551–579.

Waters, C. Kenneth (2005), Philosophy of Experimental Biology. Cambridge: Cambridge University Press.

Weber, Marcel (1999), "The Aim and Structure of Ecological Theory", in Philosophy of Science 66, 71–93.

Woodward, James (2003), Making Things Happen: A Theory of Causal Explanation. Oxford: Oxford University Press.

Woodward, James (2010), "Causation in Biology: Stability, Specificity, and the Choice of Levels of Explanation", in Biology and Philosophy, online first prepublication

Wouters, Arno G. (2003), "Four Notions of Biological Function", in Studies in History and Philosophy of the Biological and Biomedical Sciences 34, 633–668.

Wouters, Arno G (2007), "Design Explanation: Determining the Constraints of What Can Be Alive", in Erkenntnis 67, 65–80.