Garson’s book revolves around one single question: what is a biological function? The author presents us an overview of most answers provided to the question, which is a task that is complex and at times confusing but for sure, useful. Garson’s systematic, articulate and down-to-earth writing style should be praised, being effective in providing intelligibility to what is known to be an intricate topic. The author’s critical perspective and his own answer to the book’s main question are presented in last chapter.

         But let us first frame the question ‘what is a biological function’, so we can then address why is such a book relevant to ecology, philosophy of medicine, mental health professionals and researchers.

         In Biology, functions are ascribed to biology traits. But whether or not it is possible to know what a function is, how to identify it, and which criteria should be applied in order to define it, concerns to Philosophy. The main question at stake is, therefore, in the realm of Philosophy of Biology, being “the notion of function […] one of the foundational concepts of the life sciences”. (p.3) Those interested in the work of Charles Darwin (1809-1882) and theory of form, will also find this a useful reading.

Understanding what is a function is challenging because it can be easily assumed that a function is for something (teleological) and that a system works properly or in a dysfunctional way, according to the trait that is attributed to a function (normative). The question is: how can we establish the best possible criteria that allows us to be sure that that function is for ‘that’ and, that ‘that’ system is the normal functioning one. Or, more radically, should we maintain teleology and normativity as criteria of what a biological function is? If we say ‘no’, which criteria should we have instead? If we say ‘yes’, how can we maintain these as criteria if we are not able to agree on what exactly satisfy them?

         Garson states that there are three different perspectives on what should a philosophical theory of biological function be and all three involve subtle issues about language and metaphysics (p.10): a conceptual analysis, a theoretical definition and a Carnapian-style explication. Though the author focuses on the first one, whichever one is accepted, he defends that “a theory of function should be reasonably constrained by actual biological usage” (p.1)

The theory of functions is relevant, for example, to geneticists who recently formed ENCODE (ENCyclopedia Of DNA Elements) in order to debunk the claim that 10% of the human genome is functional and the rest constitutes “junk DNA”, by proving that 80% of the human genome is functional. But which understanding of “functional” is at stake here? Is the understanding too broad or too strict?

         In medicine, psychiatry and psychiatric classification, the impact of discussion or reconsideration of the connection between a trait and a function, has an immediate effect on psychiatric classification criteria. Classification is key so that an accurate diagnosis can take place. If there is any chance of a successful treatment, that starts with a good diagnosis. For example: there are debates on whether the experience of grief should be a “mental disorder” (p.2); there is a debate on whether “mental disorder” should be defined in terms of dysfunction or not and; on whether a disease should be explicated in terms of its biological function. One of Garson’s goals, in the realm of psychiatry, is to avoid negative social implications of what is perceived as “function” and “dysfunction”. (p.6)

         We now provide a quick outline of the book’s structure:

In chapter two, a discussion on naturalized teleology between the 1940s and 1960s is presented, a time when the goal-directedness approach to teleology was popular pertaining to cybernetic machines and homeostatic systems (the behaviouristic and the mechanistic). This approach allowed the emergence of the theory of functions that sustains the goal-supporting theory of functions.

Chapters three, four and five, present an overview of the three main perspectives at stake over the last 40 years: 1) ‘Selected effects theory of function’: a function of a trait is whatever it was selected for, by natural selection or some natural process of selection, which has recently a new version called ‘generalized selected effects theory’, showing how brain structures (eg. synapses) can acquire new function; 2) ‘Fitness-contribution theory of function’: the function of a trait consists in its typical contribution to the fitness of the organisms that possess it; 3) ‘The causal role theory of function’: a function of a part of a system consists in its contribution to some system-level effect, which effect has been picked out as especially interesting by a group of researchers — this perspective has a sophisticated version: ‘the mechanistic causal role theory’.

In order to clarify the content of each of these perspectives, and which are its strong and weak features, we recommend Garson’s book, which proves to be up for the task. Along the way, critical points being discussed today in the realm of psychiatry and mental health, for example, become much clearer due to Garson’s effective mapping skills.

Most philosophers agree that the ‘selected effects theory’ and ‘the causal role theory’ capture important elements of biological usage. That is why it has emerged a popular form of pluralism that accepts both theories. This is a between-discipline pluralism, that holds that ‘selected effects theory of function’ mainly captures the way evolutionary biologists use the term “function” and ‘the causal role theory’ mainly captures the way “function” is used in other disciplines. But Garson himself, proposes a new form of pluralism, a within-discipline pluralism, which emphasizes the co-existence of function concepts within any given discipline. (p.81)

         Chapter six, presents us alternative accounts of functions that have emerged in the last 20 years and the closing chapter presents us Garson’s view on the topic where he comes forward as a supporter of the ‘generalized selected effects theory’, suggesting a few modifications. Garson’s answer to the teleological and normative questions is that not all explanations are causal and that the understanding of what a function is must be plural and go beyond the area of biology.

         The author concludes by showing us the vast open horizon that this topic represents, by stating the most outstanding problems for most theories of functions showing us that when it comes to theory of functions, there is still much to discuss, making the reader aware of its relevance for the future of ecology, philosophy of medicine and mental health.

© 2017 Diana Soeiro

Diana Soeiro. Postdoctoral Research Fellow in Philosophy at NOVA Institute of Philosophy /IFILNOVA at Universidade Nova de Lisboa (Portugal). Updated information: www.linkedin.com/in/DianaSoeiro