Pre-print of: “Causality, Teleology, and Thought Experiments in Biology”, Journal for General Philosophy of Science, 2015. DOI: 10.1007/s10838-015-9293-9
The final publication is available at link.springer.com
Marco Buzzoni
CAUSALITY, TELEOLOGY, AND THOUGHT EXPERIMENTS IN BIOLOGY
Department of Humanistic Studies,
Section of Philosophy and Human Sciences
via Garibaldi 20, I-62100 Macerata - Italy
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ABSTRACT
Thought experiments (henceforth TEs) de facto play many different roles in biology: economical, ethical, technical and so forth. This paper, however, is interested in whether there are any distinctive features of biological TEs as such. The question may be settled in the affirmative because TEs in biology have a function that is intimately connected with the epistemological and methodological status of biology. Peculiar to TEs in biology is the fact that the reflexive, typically human concept of finality may be profitably employed to discover mechanical-experimental causal relations in all living beings – with the obvious caveat that we do not hypostatise and interpret this concept as an ontological quality, since this would land one in an implicitly animistic, pre-Galilean view of nature. From a methodical point of view, the concept of finality is an essential assumption as well as a powerful heuristic tool in the practice of biology, that is, in the investigation of living beings in an intersubjectively testable and reproducible way.
Keywords:
Thought experiment in biology
Teleology
Experiment
Mechanism
1. INTRODUCTION
As Ernst Mayr noted some years ago, the battle over the status of biology
“has been waged between two distinct camps. One claims that biology does not differ in principles and methods from the physical sciences, and that further research, particularly in molecular biology, will in time lead to a reduction of all of biology to physics. [...] The other camp claims that biology fully merits status as an autonomous science because it differs fundamentally in its subject matter, conceptual framework, and methodology from the physical sciences [...].” (Mayr 1988: 8)
Those who defend the first claim are faced with the puzzling fact that most biological concepts are defined in functional and teleological terms and that notably Darwin himself made use of explanations which he claimed revealed the final cause of this or that structure or behaviour (cf. Lennox 1993). To solve this problem, they have tried to show that Darwin’s teleology is only apparent, in the sense that it can be fully explained by empirical forces which are not intrinsically teleological. Even though there are many differences among these scholars, they all share the same view, which I can perhaps best express by August Weismann’s words: the “philosophical meaning” of Darwin’s theory lies in the fact that it is founded on a principle “that does not act purposefully, but nonetheless brings about what is suitable for an end” [welches nicht zwecktätig ist und doch das Zweckmäßige bewirkt] (Weismann 1902 [1904], Band I: 47).
Logical empiricists such as Ernst Nagel and Carl Gustav Hempel agreed on this interpretation of teleology in naturalistic terms (cf. Nagel 1961 and 1977, Hempel 1965). In the following years, this view gained further support. In 1986, Dawkins based his definition of biology on this idea: biology is “the study of complicated things that give the appearance of being designed for a purpose.” (Dawkins 1986 [1996]: 1; italics added.) And the same applies, in the last analysis, to the various versions of the etiological theory of proper functions.[1]
In my opinion, one of the most interesting efforts to reconcile teleology with efficient causality (without claiming for organisms an objective teleological constitution[2]) is still that of Ernst Mayr. Even though, as we shall see shortly, Mayr’s influential attempt was not entirely successful, it contained an important element of truth, which was reiterated more recently by Paul S. Agutter and Denys N. Wheatley (1999). Expressly following, and even building on Mayr’s viewpoint, Agutter and Wheatley maintained that function-statements are not only scientifically acceptable in biological discourse but they also “have (or can have) a positive and irreplaceable scientific role. Perhaps, therefore, we should conclude that function-statements are not merely acceptable in biology, but are indispensable in their way to its continued progress.” (Agutter and Wheatley 1999: 21)
Unfortunately, however, this important thesis is insufficiently justified, since it only gets a few marginal remarks at the end of the paper. Besides, it is strongly attenuated by the “perhaps” clause. For these reasons, Agutter and Wheatly fail to relieve biologists from their discomfort in using a teleological vocabulary. In this paper I shall argue that there is no reason to invoke the “perhaps” clause, provided the methodical function of teleology is rightly understood. In order to do this, however, the deep connection between the epistemological and methodological status of biology and the nature of thought experimentation also needs to be grasped. (In what follows I shall use the word “methodical” to denote the methods which can be used as means to a cognitive end, such as Descartes’s “methodical doubt” can exemplify; and “methodological” to denote the discourse on the methods, in a sense which applies to, say, a textbook on methods.)
My main working hypothesis will be that a distinctive characteristic of biological TEs is that they exploit the reflexive, typically human concept of finality in order to discover causal mechanisms in the living world. In other words, teleology, if connected with thought experimentation, not only can but perhaps should be used to generate scientific predictions in the most usual sense of the word “science”.
1. TELEOLOGY, MACHINES, AND SCIENTIFIC EXPERIMENT
Against a certain rather widespread prejudice, I shall argue in this section that the ‘mechanistic’ and the ‘teleological’ point of view are are intimately connected. This section is intended to shake up this very common prejudice and dispose the reader to consider on its merits the following positive argument for using teleology in biological investigations. I will give two arguments: the first represents mechanisms as revealing an implicit teleological structure, the second shows that teleology is at the heart of the notion of scientific experiment.
First, contrary to the most widespread notion of mechanism (or machine), it should be noted that the attempt to describe and define a mechanism (or a machine) merely as a system that changes regularly from initial to terminating conditions is doomed to fail.[3] We identify a machine or a mechanism by its operational principles. These principles delimit what a mechanism is capable of doing, what its purpose is, and how we are to evaluate its efficiency or usefulness in achieving that purpose. As Polanyi noted, machines
“can be recognized as such only by first guessing, at least approximately, what they are for and how they work. Their operational principles can then be specified further by technological investigations. Physics and chemistry can establish the conditions for their successful operation and account for possible failures, but a complete specification of a machine in physical-chemical terms would dissolve altogether our knowledge of the machine.”[4]
The idea that final causes are, in a fundamental epistemic sense, the condition of the possibility of mechanical ones may be made clearer by considering the concept of scientific experiment. Purposes may be seen as concepts or meanings guiding us in our practical activities. In this strict sense, the concept of an aim or a purpose characterizes only human actions. However, it would be radically false to say that purposes play no part in the explanation of natural phenomena. It is only by reference to the implicit teleology of experimental ‘machines’ or ‘mechanisms’ that we are able to give reliable experimental-mechanistic explanations.
Following Kant’s suggestion, experimentation may be considered as a ‘question put to nature’ (Frage an die Natur)[5], and the answer to an experimental question is discovered by applying the method of deliberate and systematic variation which requires an active intervention on natural processes. Scientists in principle perform free repeatable actions and they intentionally modify independent variables in a way that is reproducible in order to determine the consequences of these modifications on one or more dependent variables. More precisely, on the one hand experimenting involves an ‘external’ realization ˗ the construction of an ‘experimental machine’ ˗, which extends the original operativity of our organic body, and, thereafter, develops independently of the subject and ‘impersonally’. On the other hand, in an experiment, an initial free action is necessarily presupposed, guided by the conception of a (cognitive) end. Apart from teleology, apart from the intentional and conscious planning of an experimental set-up and apart from the human actions which freely start or ‘set in motion’ the experimental machine, it would be impossible to identify causal relations in nature. And this is tantamount to saying that scientific experiments can only be understood in relation to the human norms and purposes in the light of which they are freely performed. In a word, there is no scientific knowledge without experimenting and there is no experimenting without our free agency, that is, without the free interaction between our body and the surrounding empirical reality according to some cognitive purposes.[6]
We conclude, therefore, that the very nature of scientific experiment demonstrates that teleology and efficient-mechanical causality are not only compatible but that final causes are actually the condition of the epistemic possibility of mechanical ones, since without our knowledge of final causes there would be no experiment and therefore no imputation of mechanical causes (this is not to deny that causality has also an ontological side, but I cannot go into this controversy here).[7]
In biology, as I shall show in the next section, this teleological moment is not only an essential presupposition of any causal imputation, but, unlike in physics, it is also a general-methodical (and in some sense counterfactual) assumption that is intimately connected both to the epistemological and methodological status of biology as a science and to the most important function performed by TE in biology. Or, putting the matter in a somewhat simplified way, it constitutes a powerful heuristic-methodical device to investigate living beings in the intersubjectively testable and reproducible way typical of Galilean science.
2. MECHANISM, TELEOLOGY, AND THE LIVING ORGANISM AS THE METHODICAL POINT OF VIEW OF BIOLOGY.
As mentioned above, Ernst Mayr made a very influential attempt to reconcile teleology with mechanism. To mediate between the two domains, Mayr used the fundamental distinction between “proximate causes”, which are the essential ingredient of biophysical explanations, and “ultimate causes”, which are the main concern of the evolutionary biologist.[8] Proximate causes, he writes, “govern the responses of the individual (and his organs) to immediate factors of the environment, while ultimate causes are responsible for the evolution of the particular DNA code of information with which every individual of every species is endorsed.” (Mayr 1961, p. 1503)
Although this distinction raises many questions and is differently understood by different authors (cf. Ariew 2003, Laland et al. 2012, Calcott 2013, Gardner 2013, Haig 2013, Watt 2013), according to some scholars, with whom I agree, Mayr’s proximate-ultimate distinction also matches the causal-teleological distinction,[9] or expressing the matter in a slightly different way, the old problem concerning the autonomy of biology towards physico-chemical experimental investigations. According to Mayr, the teleological way of speaking ought not to be translated in terms of immediate and mechanistic causes, but in Darwinian, historical-evolutionary terms:
“[T]he same event may have entirely different meanings in several different conceptual domains. The courtship of a male animal, for instance, can be described in the language and conceptual framework of the physical sciences (locomotion, energy turnover, metabolic processes, and so on), but it can also be described in the framework of behavioural and reproductive biology. And the latter description and explanation cannot be reduced to theories of the physical sciences. Such biological phenomena as species, competition, mimicry, territory, migration, and hibernation are among the thousands of examples of organismic phenomena for which a purely physical description is at best incomplete if not irrelevant” (Mayr 1988: 62-63).
In other words, no physical or chemical analysis, even if it were provided by an ideally completed physics or chemistry, could give a satisfactory explanation of the function of the behaviour of, e.g., a mating bird. Thus, Mayr rejected the view that the conceptual framework of biology could be entirely reduced to that of the physical and chemical sciences: “It is necessary for the completion of a causal analysis to ask for any feature, why it exists, that is what its function and role in the life of the particular organism is.” (Mayr 1974, p. 108; italics added)
In Mayr’s opinion, however, the “ultimate causes” of biology, even though characteristic of evolutionary biology, are not to be confused with Aristotle’s final causes. For this purpose he introduced the well-known distinction between teleomatic-mechanical and teleonomic processes and revisited the argument mentioned in the introduction to this paper:
“teleonomic processes […] are "end-directed" even though very often the "end" is the maintenance of the status quo. There is nothing metaphysical in any of this because, so far as these processes are accessible to analysis, they represent chains of causally interrelated stimuli and reactions, of inputs and of outputs. The ultimate causes for the efficiency and seeming purposefulness of these living systems were explained by Darwin in 1859. The adaptiveness of these systems is the result of millions of generations of natural selection. This is the mechanistic explanation of adaptiveness, as was clearly stated by Sigwart”.[10]
However, this argument is not fully compatible with Mayr’s conviction that “ultimate causes” ground the autonomy of evolutionary biology. A “mechanistic explanation of adaptiveness” seems to imply a mechanistic explanation of teleonomic processes, thus confirming Nagel’s remark that there is no distinction in principle between teleonomic and teleomatic processes.[11] Were it possible to reduce ultimate causes and teleonomic or goal-directed processes in every sense to proximate causes and teleomatic processes, the autonomy of evolutionary biology would be merely apparent. And vice versa, if evolutionary biology was thought of as an autonomous research field characterized by the use of “ultimate” causes concerning “teleonomic” processes, it should be possible to specify a sense in which “ultimate” causes are not entirely reducible to physico-chemical causes. In the last analysis, Mayr’s solution remains eclectic and cannot steer his course safely between the Scylla of Aristotelian finalism and the Charybdis of reductionist mechanism.[12]