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Rethinking Biological Functions: A Goal-Contribution Approach and Its Systemic Implications
Hanzhe Dong and Gualtiero Piccinini, University of Missouri
Cross-posted at Dialectical Systems
Introduction: The Role of Functions in Biology and Philosophy
Biological functions play a critical role in our understanding of living organisms and their traits. Whether we’re talking about the heart, lungs, or brain, their “function” helps an organism survive, grow, reproduce, and sometimes assist others. But can we explain more precisely what a biological function is? Can functions distinguish between what a trait does and what it ought to do? These questions have been debated for decades, and they have crucial implications for biologists and researchers in other fields. In this article, we’ll explore different ways of thinking about biological functions, with a focus on how these views can help us make sense of living systems.
There are several accounts of functions. Two prominent accounts, which have dominated the philosophical literature since the 1980s, are the causal role account and the selected effects account. The causal role account posits that a function is any causal role a trait or mechanism plays within a complex system. For instance, the heart’s contraction and generation of pressure waves are functions because they are causal roles it performs (Cummins, 1975). In contrast, the selected effects account ties functions to evolutionary history or some other form of selection. It suggests that a function is a causal role that a trait has been selected for. According to this view, the heart’s function is to pump blood because hearts that pumped blood effectively were selected for in our ancestors, leading to the hearts we have today (Millikan, 1984; Neander, 1983; Garson 2019). In contrast, the heart’s generation of pressure waves was not selected for, so it’s not a function according to a selectionist account.
Limitations of Traditional Accounts
While both accounts offer valuable insights, they face significant limitations, especially when considering the teleological nature of biological functions. The causal role account is broad and inclusive, recognizing any causal role as a function. This inclusivity becomes problematic because it doesn’t differentiate between causal roles that are intuitively functional and causal roles that are not functional and may even be dysfunctional. For example, neurons generate electrical signals and produce heat. According to the causal role account, both are functions because they are causal roles performed by neurons. However, we intuitively recognize signal transmission, not heat production, as the neuron’s genuine function. The causal role account cannot make this distinction because it treats all causal roles equally.
The selected effects account focuses on selection history, adding an explanatory layer by connecting functions to selection. However, it introduces its own set of problems. Consider a novel mutation that allows a bacterium to digest a new type of sugar. This trait significantly contributes to the bacterium’s survival but hasn’t been selected for yet—it just appeared. According to the selected effects account, this trait doesn’t have a function until it has been selected over generations. This seems counterintuitive because the trait is clearly functional in aiding the bacteria’s survival immediately (Garson, 2019). Moreover, the selected effects account struggles with artifacts and tools designed by humans or animals. A newly invented gadget hasn’t been selected for through evolutionary processes but may serve a clear function.
A New Perspective: The Goal-Contribution Account
To address these limitations, a new twist on the goal-contribution account offers a fresh perspective. Previous goal-contribution accounts (e.g., Boorse 1977) understood functions in term of a trait’s contribution to a goal, where the pursuit of goals is cashed out in terms of goal-directed systems. That faces some problems. One problem is that a system being goal-directed does not seem either necessary or sufficient for a trait to have functions. Another problem is that it seems difficult to give an adequate account of malfunction in terms of a trait’s individual contribution to a goal (Kingma 2016).
A more recent version of the goal-contribution account understands biological functions as regular contributions to organisms’ goals by a type of trait, without requiring that everything that contributes to goals be goal-directed, without necessarily tying functions to selection history, and without treating all causal roles equally (Maley & Piccinini, 2017). At the core of this account is the idea that biological functions are teleological—they are directed toward achieving specific biological goals that populations of organisms must pursue to continue existing. These goals include survival (maintaining internal structure and staying alive), development (growing and maturing into a fully functional organism), reproduction (generating offspring to continue the species), and helping (assisting others, which can include offspring, relatives, and unrelated organisms including members of other species) (Piccinini, 2020).
Organisms expend energy and resources to pursue these goals, and mechanisms within them contribute to these goals in regular and reliable ways. In this framework, organisms are not just made of parts performing any causal role; they are teleofunctional systems whose parts contribute to the organisms’ biological goals. For example, the heart’s function is not merely to contract but to circulate blood throughout the body, directly contributing to survival and development by delivering oxygen and nutrients to cells. Similarly, the lungs function to facilitate gas exchange, providing oxygen to the blood and removing carbon dioxide—an essential process for survival.
A key aspect of the goal-contribution account is that functions must be performed regularly and reliably at appropriate rates under appropriate conditions (Garson & Piccinini, 2014). This criterion excludes random occurrences from being considered functions. For instance, suppose someone gets a headache, which leads them to seek pain killers at a pharmacy, and that saves their life because while they are at the pharmacy, their office is blown up by a bomb. This random coincidence does not turn headaches into traits with the function of saving people from bomb attacks.
By narrowing the scope from all causal roles to those serving biological purposes, the goal-contribution account distinguishes between functions and incidental effects based on their contribution to the organism’s goals. While neurons produce heat as a byproduct of their activity, this heat generation is incidental. The biological function of neurons is to transmit electrical signals, contributing to information processing—a critical aspect of many organisms’ survival and interaction with their environment. The causal role account cannot differentiate between a neuron’s essential function of signal transmission and its incidental heat production because both are causal roles. The goal-contribution account makes this distinction by considering only the roles that contribute to biological goals.
While the selected effects account relies on selection history to define functions, the goal-contribution account focuses on immediate contributions to biological goals, regardless of whether the trait was historically selected for. It accommodates novel traits or behaviors that clearly serve a function but haven’t yet been subject to selection. This approach aligns with our intuitive understanding that traits can be functional in aiding an organism’s survival or reproduction, even if they are new and haven’t undergone selection (Garson, 2019).
In the goal-contribution account, a malfunction occurs when a mechanism fails to perform its teleological function at an appropriate rate in an appropriate situation, thus failing to contribute to the organism’s goals (Piccinini, 2020). For example, if the heart cannot pump blood at the necessary rate, it malfunctions because it fails to contribute to the organism’s survival and development. This judgment is based on the function’s role in pursuing biological goals, not on whether the trait was selected for in the past. By focusing on the organism’s goals, the account introduces a sense of normativity, allowing us to judge whether a trait is functioning properly based on its contribution to these goals, independent of selection history.
An important aspect of this account is recognizing that organisms have limited resources and must prioritize certain functions over others in different situations. Functional tradeoffs occur when performing multiple functions requires shared resources, necessitating the prioritization of some functions over others (Piccinini, 2020). For example, during strenuous exercise, blood flow is directed to muscles rather than the digestive system. As a result, digestion might slow down—a functional tradeoff prioritizing immediate needs over digestion. In this context, the slowed digestion is not a malfunction but an appropriate response to the organism’s goals.
By not requiring a trait to have been selected for, the goal-contribution account is more flexible and applicable to a wider range of cases. It accommodates new mutations or traits that arise and immediately contribute to an organism’s goals, as well as artifacts and tools created by organisms that serve a function but haven’t been subjected to selection. This account aligns functions with the overall organization and goals of organisms, emphasizing the interconnectedness of mechanisms and how they work together to achieve biological goals.
In short, the goal-contribution account provides a compelling alternative to previous theories by focusing on the regular contributions that traits and mechanisms make to an organism’s biological goals. It captures the teleological character of biological functions, recognizing the goal-directed nature of living organisms and the mechanisms that support them. This approach aligns closely with our intuitive understanding of function and malfunction, accommodates novel and unselected traits, and emphasizes the systemic nature of biological functions.
Organismic/Systemic Accounts: Teleology in Living Systems
In addition to the goal-contribution account, another influential perspective on biological functions is the organismic or systemic account, which emphasizes the role of organizational closure and self-maintenance in living systems. According to this account, functions are defined as the contributions that parts of an organism make to the maintenance of the system’s organization, characterized by a network of mutually dependent processes and structures (Mossio et al., 2009). This organizational closure means that each component both depends on and contributes to the system’s overall functioning, creating a self-sustaining loop that defines the organism’s identity and persistence over time. As Mossio and Bich (2017) point out, this systemic teleology arises from the regulatory control that characterizes biological organization, which in turn grounds the teleology of individual functions. Such an account places the organism’s organization at the center of function attribution, connecting systemic self-maintenance to the teleological nature of its parts (Bich, 2024).
Organizational closure refers to the mutual dependence of an organism’s parts, where each part sustains the system’s overall organization, and in turn, the system sustains the part. This concept captures the intricate interplay between various components of a living system, highlighting how their coordinated activities contribute to the organism’s self-maintenance (Saborido et al., 2011). For example, the heart’s function is not merely to contract but to pump blood, thereby circulating nutrients and oxygen essential for the organism’s survival. This contribution supports the maintenance of the organism’s internal environment, which in turn supports the heart’s own existence—a mutual dependence that exemplifies organizational closure (Mossio et al., 2009).
The organismic account grounds the teleological nature of functions in this organizational closure. Functions are not ascribed based on selection history but are determined by how a trait contributes causally to the persistence of the system’s organization. This approach aligns with the view that biological systems are characterized by their capacity for self-production and self-maintenance, existing in far-from-equilibrium conditions that require continuous input and processing of energy and matter (Mossio et al., 2009). In this sense, functions are immediate and systemic, centered on the organism’s present organization rather than its selection history.
Normativity and malfunction are also integral to the organismic account. A malfunction occurs when a trait fails to contribute appropriately to the system’s maintenance, disrupting the organizational closure (Saborido et al., 2011). For instance, if the heart cannot pump blood effectively, it is malfunctioning because it no longer supports the organism’s self-maintenance. This normativity is inherent in the system’s organization and does not rely on external factors or historical selection processes.
Compatibility of the Goal-Contribution and Systemic/Organismic Accounts
The goal-contribution account is compatible with the organismic or systemic account insofar as organisms’ self-maintenance and self-production, which lie at the core of the organismic/systemic account, are equivalent to survival and development (and maybe reproduction), which are biological goals recognized by the (new) goal-contribution account. The goal-contribution account is more focused on how organisms are mutually interdependent, so it recognizes reproduction and mutual help as biological goals. Insofar as the organismic/systemic account does not recognize regular contributions to reproduction and helping others as functions, the goal-contribution account is more inclusive, and the organismic/systemic account may be seen as a component of the goal-contribution account. In any case, the two accounts seem to us (mostly) compatible and complementary.
Both perspectives emphasize that functions are teleological. The goal-contribution account focuses on how mechanisms contribute to biological goals such as survival, development, reproduction, and helping others (Piccinini, 2020). Similarly, the organismic account considers how components contribute to the self-maintenance of the organism’s organization, which is essential for achieving these biological goals.
In both accounts, normativity arises from traits’ relation to the organism’s survival and self-regulation. The goal-contribution account bases normativity on whether a trait effectively contributes to the organism’s goals, while the organismic account grounds it in the trait’s role in maintaining organizational closure. Despite this slight difference in emphasis, both approaches assess the function of a trait based on its current causal contribution.
Consider the function of the lungs: In the goal-contribution account, the lungs function to facilitate gas exchange, providing oxygen to the blood and removing carbon dioxide, thereby contributing to the organism’s survival—a primary biological goal. In the organismic account, the lungs’ function is to maintain the organism’s internal organization by ensuring that cellular respiration can occur, which is necessary for the energy production that supports all bodily functions (Mossio et al., 2009). Both accounts recognize the lungs’ role in contributing to systemic processes essential for the organism’s persistence.
Moreover, both accounts address the issue of malfunction similarly. A trait malfunctions when it fails to perform its function in a way that supports the organism’s goals or organizational maintenance. This shared understanding reinforces the compatibility between the goal-contribution and organismic accounts. For example, if a trait like the heart fails to pump blood at an appropriate rate, both accounts would consider it a malfunction due to its failure to contribute to survival and self-maintenance (Saborido et al., 2011).
Some Recent Developments in Biological Function Theory
Some recent developments in biological function theory provide new insights that align closely with the goal-contribution account and the organismic/systemic perspective. One contribution comes from Brandon Conley’s dispositionalist approach to malfunction. Dispositionalism (i.e., the causal role account) has historically struggled with explaining malfunction, as it seemed to imply that an item lacking the capacity to perform a function no longer retains that function. Conley’s work addresses this issue by reframing malfunction as a failure to play the same role that is played by similar items within similar systems. He argues that functions are best understood in relation to their contributions to the organism’s systemic capacities and lack thereof, even in cases where performance is impaired. Thus, a system or trait can still have a function even if it is malfunctioning because it retains its role within the broader systemic organization of the organism (Conley, 2023).
Conley’s approach is highly compatible with the goal-contribution account, which emphasizes traits’ contribution to survival, development, reproduction, and helping others. For instance, even in cases where the heart is failing, it still has the function of pumping blood because hearts in general contribute, sometimes inadequately, to the organism’s goal of survival. This understanding allows for a nuanced view of malfunction as occurring along a continuum, where the failure of a system to fully meet its goals does not negate the trait’s functional status but instead marks it as impaired. This model mirrors the goal-contribution account’s focus on how mechanisms continue to contribute to biological goals, even under suboptimal conditions.
In a related development, Andrew Rubner’s 2024 dissertation offers an ahistorical account of natural functions, particularly in the context of perceptual systems. Rubner argues against the traditional selected-effects account, which ties functions to traits that were selected for. Instead, he proposes that functions should be understood in terms of their current contributions to goals. This view aligns strongly with the goal-contribution account’s emphasis on how traits and mechanisms serve biological goals regardless of their evolutionary background (Rubner, 2024).
Rubner’s focus on perceptual systems—like vision—illustrates how these systems serve the organism by processing information critical to its immediate survival. For instance, vision allows organisms to navigate their environment and avoid predators, a contribution directly related to survival, which is a key biological goal in the goal-contribution account framework. Rubner’s argument extends the goal-contribution account’s application beyond physical mechanisms to include cognitive and perceptual functions, emphasizing that functions are defined by their present contributions rather than their selection history.
These recent proposals enhance the systemic understanding of biological functions. Both Conley and Rubner offer models that reinforce the idea that functions are about current contributions to the organism’s capacities or goals. Conley’s dispositionalist account of malfunction aligns well with the goal-contribution account by showing that traits can still possess functions even when impaired. Similarly, Rubner’s ahistorical perspective complements the goal-contribution account’s teleological focus by arguing that functions can be ascribed to traits that fulfill current biological goals, independent of their evolutionary past.
These perspectives also reinforce the normative dimension of the goal-contribution account and systemic account, where malfunction is defined in terms of failing to meet an organism’s goals, rather than selection history. When a trait such as the heart or lungs fails to contribute effectively to survival or systemic maintenance, both the goal-contribution account and these recent proposals recognize this as malfunction, not because of selection pressures, but because the trait fails to provide its normal contribution.
Together, Conley’s and Rubner’s contributions offer a flexible, real-time understanding of biological function. Their work builds on the goal-contribution account’s foundation, emphasizing that functions should be understood in relation to the ongoing contributions they make to an organism’s survival (which includes systemic maintenance), development, reproduction, or other goals. By extending the concept of function beyond selection history and focusing on present utility, these recent contributions provide a robust framework for understanding biological functions that align with the goal-directed, systemic nature of living organisms.
Conclusion
In conclusion, the goal-contribution account and the organismic or systemic account offer complementary perspectives on biological functions. Both recognize the teleological nature of functions, emphasize the importance of a trait’s contribution to the organism’s goals or self-maintenance, and ground normativity in the immediate functioning of the organism rather than in evolutionary history. By aligning functions with the organism’s present organization and goals, these accounts provide a coherent and comprehensive framework for understanding biological functions that are both systemic and organism-centered. This is a valuable alternative to the more traditional causal role and selectionist accounts, which have dominated the literature for so long. It may provide a better foundation for many biological and mind sciences than those more traditional accounts (Piccinini, 2020).
References
Bich, L. (2024). Organisational teleology 2.0: Grounding biological purposiveness in regulatory control. Ratio, doi:10.1111/rati.12405
Conley, B. A. (2023). Dispositionalism and Dysfunction. Philosophy of Science, 90(3), 686–703. doi:10.1017/psa.2023.30
Cummins, Robert E. (1975). Functional analysis. Journal of Philosophy 72 (November):741-64.
Garson, J. (2019). What Biological Functions Are and Why They Matter. Cambridge: Cambridge University Press.
Garson, J., & Piccinini, G. (2014). Functions Must Be Performed at Appropriate Rates in Appropriate Situations. The British Journal for the Philosophy of Science, 65(1), 1–20. http://www.jstor.org/stable/24562864
Kingma, E. (2016). “Situation-Specific Disease and Dispositional Function.” The British Journal for the Philosophy of Science 67: 391–404.
Maley, C. J., & Piccinini, G. (2017). A Unified Mechanistic Account of Teleological Functions for Psychology and Neuroscience. In D. M. Kaplan (Ed.), Explanation and Integration in Mind and Brain Science. Oxford University Press.
Millikan, R. G. (1984). Language, Thought, and Other Biological Categories: New Foundations for Realism. Cambridge, MA: MIT Press.
Mossio, M., and Bich, L. (2017). What makes biological organisation teleological? Synthese, 194(4), 1089-1114.
Mossio, M., Saborido, C., & Moreno, A. (2009). An Organizational Account of Biological Functions. The British Journal for the Philosophy of Science. https://doi.org/10.1093/bjps/axp036
Neander, K. (1983). Abnormal Psychobiology. Ph.D. dissertation, La Trobe.
Saborido, Cristian; Mossio, Matteo & Moreno, Alvaro (2011). Biological Organization and Cross-Generation Functions. British Journal for the Philosophy of Science 62 (3):583-606.
Piccinini, G. (2020). Neurocognitive mechanisms: Explaining biological cognition. Oxford University Press. https://doi.org/10.1093/oso/9780198866282.001.0001
Rubner, Andrew. (2024). Natural function and perceptual content. Ph.D. Dissertation. Retrieved from https://doi.org/doi:10.7282/t3-jhbd-6237
This is really good stuff Gualtiero. I’ve always felt an affinity to this kind of view, partly because it fits with how ascribe functions in biology in practice: we don’t typically do evolutionary deep dives when thinking about function of something that has clear contributions to the goals and “well being” of an organism.
I do wonder if there is room for pluralism here. There are some traits like bee stinging that causes death, eusociality, and other things that are (at least on the surface) really hard to explain by reference to individual organism goals etc. For those, it seems the more historical evolutionary perspective might be needed.
Thanks Eric, there’s definitely room for pluralism on functions. I’ve long believed that there are many useful notions of function in biology and engineering. I just think that the goal-contribution account captures the core notion that is most useful to understand systems here and now.
I’m all in for the goal-contribution account, except for the relinquishing of selection, and the apparent focus on goal of system survival. Seems to me that the point of discussing biological functions is to develop an explanation for why a system exists in most/all examples of a population. You can ascribe function to a brand new trait (i.e., a variation), but you are essentially saying that the new variation is an affordance for selection. As for system survival, what about when a system adopts the sub-goal of anti-survival? (Suicide). Does that make the functions of the subsystems in pursuit of that goal (like, finding a gun, feeling the trigger, proprioceptively pointing the gun) malfunctions, since their use is counter to the goal of survival?
My point is that ascribing function probably always entails selection (could be wrong), and that any goal which is used for such selection is sufficient to ascribe function.
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Thanks James, great point. In my published work I talk a bit about the fact that some creatures can choose and pursue goals that go beyond basic biological goals (e.g., pleasure, knowledge, and even death). These are non-biological goals, and functions can be defined relative to them. So the account generalizes, but we need to tell a story about how all these goals (biological and non-biological) relate to one another. There is room for more good work in this area.