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  • On the Theoretical Motivation for Positing Etiological Functions
  • Björn Brunnander (bio)

I Introduction

It is a plain fact that biology makes use of terms and expressions commonly spoken of as teleological. Biologists frequently speak of the function of biological items. They may also say that traits are 'supposed to' perform some of their effects, claim that traits are 'for' specific effects, or that organisms have particular traits 'in order to' engage in specific interactions. There is general agreement that there must be something useful about this linguistic practice but it is controversial whether it is entirely appropriate, and if so why it is.

Many theorists have defended the use of seemingly teleological terms by appeal to an etiological notion of function (Wright, 1973; Millikan, 1984, 2002; Neander, 1991; Griffiths, 1993; Godfrey-Smith, 1994; and Buller, 1999). According to the etiological notion, attributing a function to a trait is a matter of pointing to effects that account for why the trait has been selected for. On an alternative but related formulation function statements indicate that past tokens of the targeted type contributed to the existence of current token traits in virtue of exhibiting the effect at issue. A central feature of etiological definitions is that they come with a requirement of ancestry; there must have been type-identical tokens exhibiting the targeted effect in order for a trait [End Page 371] to have an etiological function. Trivially, first-generation tokens lack such ancestors as far as the novel trait is concerned and therefore lack etiological functions.

In this paper, I will home in on the theoretical motivation for the requirement of ancestry, a requirement that renders the resulting functions essentially etiological. I will argue that the positing of etiological functions is theoretically ungrounded. Not that there aren't any tokens that meet the description, but this is far from sufficient. So, for instance, there is a real difference between tokens with a trait T that are born 2000 years or more after the first token with T, and tokens that are born earlier. We may then add to a standard etiological definition of 'function' the requirement of being born 2000 years or more after the first mutant and let 'munction' stand for the resulting historical property. Are there munctions? Well, if all that is required in order to answer affirmatively is that there are tokens that fit the description then the answer is clearly 'yes.' However, there is no known reason for stressing that particular difference and therefore no reason to posit munctions. Likewise, the point of this paper is that there is no theoretical reason to stress the difference between first-generation tokens and later ones and thus no reason to conceive of biological functions as essentially etiological.

There is nothing new about voicing negative verdicts about etiological accounts of 'function' (Cummins, 1975, 2002; Enç and Adams, 1992; Walsh and Ariew, 1996; Davies, 2000a, b; McLaughlin, 2001; Lewens, 2004). I take my approach to differ from, and be a useful complement to, that of others in the following respects: I press the question of the rationale for the exclusion, by definition, of first-generation tokens more consistently than has been done elsewhere. I attempt to run through the main considerations etiologists have brought to bear on the topic. In the process I look into the claim that the etiological notion of function is required for biological categorisation, and critically address relatively recent proposals made by etiologists on this issue. I look at Millikan's (1984) explicit motivation for her 'proper function' — that it is required to capture explanatory analogies between domains — and find that this motivation fails to suggest an etiological notion as opposed to a non-etiological one. I provide a rather thorough critical discussion of the idea, made popular by Wright (1973), that the etiological notion is vindicated by its role in explaining the existence of traits. I also discuss the possibility of finding support for the etiological account in the writings of prominent biologists and conclude that the textual evidence is not unequivocally in favour of an etiological account. All things considered, I take my account to strongly suggest that the etiological account of functions gets...