Is Internal/External Eternal?

Guest blogger Trevor Pearce writes...

One of Stephen Jay Gould’s boldest claims (and that’s saying something) was that paleontology boils down to three eternal questions:

1) “Does the history of life have definite directions; does time have an arrow specified by some vectorial property of the organic world”?

2) “Does the external environment and its alterations set the course of change, or does change arise from some independent and internal dynamic within organisms themselves?”

3) “What is the tempo of organic change? Does it proceed gradually in a continuous and stately fashion, or is it episodic?”

Gould argued that these questions were asked before Darwin and had persisted to the late 1970s. Geologists, paleontologists, and evolutionary biologists seemed to be stuck with them (Gould 1977, 1-3).

Rather than exploring Gould’s chapter in detail, I want to focus on the second of his questions, giving a selective overview of its role in the history of the philosophy of biology. Both in the late nineteenth century and more recently, philosophers have relied on the internal/external dichotomy to frame their picture of evolution. Although philosophers sometimes think that careful conceptual analysis is the only way forward, the historical record suggests that we might do better to ask what sort of evidence can show that some particular factor “sets the course” of evolutionary change.

Drawing on historical work by Dov Ospovat, Gould’s chapter explained that nineteenth-century geologists thought external circumstances—especially climate—dictated the presence of certain types of organisms. Charles Lyell even suggested that if conditions were right, “the huge iguanodon might reappear in the woods, and the ichthyosaur in the sea,” which prompted immediate ridicule (Lyell 1830, 123; Ospovat 1977, 329-330).

Others, like Robert Chambers—author of Vestiges of the Natural History of Creation—pointed instead to an internal dynamic connected with embryological development: “the idea . . . is, that the simplest and most primitive type . . . gave birth to the type next above it, that this again produced the next higher, and so on” (Chambers 1844, 222).

de la Beche's response to Lyell's idea that if the environments of the past re-emerged their extinct biota would too...

de la Beche's response to Lyell's idea that if the environments of the past re-emerged their extinct biota would too...

Some of the first philosophers who were interested in evolutionary ideas realized that internal/external wasn’t necessarily either/or. George Henry Lewes, criticizing Lyell as well as Chambers, emphasized “the cardinal fact that Organization is the resultant of two factors—the organism and the external conditions” (Lewes 1851, 996). Lewes’s friend Herbert Spencer, popularizer of the term ‘environment’ and progenitor of modern organism-environment talk, built his psychological theory around the extension of this idea from biological to mental organization: “all mental phenomena are incidents of the correspondence between the organism and its environment” (Spencer 1855, 584; Pearce 2010, 2014b).

Later in the nineteenth century, a number of philosophers appropriated Spencer’s organism-environment framework even as they opposed his broader approach. Francis Ellingwood Abbot used Spencer’s dichotomy to classify a variety of philosophical positions:

Is the Organism purely the product of the Environment? Then we have Empiricism, Sensationalism, Materialism . . . . Is the Environment the product of the Organism? Then we have Transcendentalism, Egoism, Idealism . . . . Are the Organism and Environment both products of some underlying and active Unity? Then we have Identity or Pantheism . . . . Are the Organism and Environment given simply in the co-ordination and correlation of actual knowledge? Then we have Dualism, Natural Realism, Positivism. (Abbot 1866, 249-250)

William James, summarizing the approach of John Dewey and his colleagues at the University of Chicago, anticipated a central aspect of Richard Lewontin’s dialectical biology:

Like Spencer, . . . Dewey makes biology and psychology continuous. “Life,” or “experience,” is the fundamental conception; and whether you take it physically or mentally, it involves an adjustment between terms. Dewey’s favorite word is “situation.” A situation implies at least two factors, each of which is both an independent variable and a function of the other variable. Call them E (environment) and O (organism) for simplicity’s sake. They interact and develop each other without end; for each action of E upon O changes O, whose reaction in turn upon E changes E, so that E’s new action upon O gets different, eliciting a new reaction, and so on indefinitely. The situation gets perpetually “reconstructed,” to use another of Professor Dewey’s favorite words, and this reconstruction is the process of which all reality consists. (James 1904, 2; Pearce 2014a)

Why should philosophers of biology and paleontology care about this history? As Peter Godfrey-Smith argued way back in the 1990s, these nineteenth-century currents still shape how biologists and philosophers frame evolutionary history (Godfrey-Smith 1996). It’s hard to think about macroevolution without considering what PGS called “externalism”—the idea (recalling Gould’s words) that “the external environment and its alterations set the course of change.”

For example, take one of Gould’s own interests, constraints in evolution—that is, factors that bias the production (as opposed to the preservation) of variants. The selective environment can only work with the variation presented to it, and champions of constraints suggest that the course of change is often set by available variation (limited by phylogenetic history, biomechanics, developmental circuitry, etc.) rather than by the external environment (Amundson 1994; Pearce 2011b). Philosophers of biology have also discussed homoplasy, the independent evolution of similar traits: Gould and other anti-externalists think that most cases of homoplasy will turn out to be parallel modifications of similar genetic/developmental material as opposed to true convergence, suggesting that the external environmental isn’t all-powerful (Powell 2012; Pearce 2012; Currie 2014). Finally, both philosophers and biologists have been excited lately about “niche construction” and “ecosystem engineering.” Even if you’re a dyed-in-the-wool externalist, it might be helpful to understand how organisms themselves create and maintain physical environments (Laland and Sterelny 2006; Barker 2008; Erwin 2008; Pearce 2011a; Barker and Odling-Smee 2014).

If Gould was right, such debates are endless, and in some sense irresolvable. Besides, extreme externalism (few opt for the other extreme these days) seems like a straw man. Surely everyone now admits both internal and external factors in evolution—Lewes was already making this point in the early 1850s! Nevertheless, there always seems to be a chorus of voices arguing that this or that evolutionary factor (constraints, ecosystem engineering, etc.) is unimportant, especially when compared to natural selection—think of your favorite critic of extended adaptationism (Barker 2008) or the extended synthesis (Pigliucci and Müller 2010).

One role for philosophers in these debates is making sure we have coherent, useful definitions of the various concepts involved. But I think we can do more: we should also ask what would count as evidence of the relative importance of some factor—what sort of experiment, what kind of paleontological data, what type of modeling result. Some folks are already doing this: I saw a nice paper by Karen Kovaka at POBAM 2016 where she called for exactly this sort of shift from theoretical to evidential questions, arguing that we don’t yet have adequate experimental evidence to determine the importance of the Baldwin Effect and related processes in evolution. But even if her approach becomes more widespread, difficult questions remain: If something is a proven factor in a specific case, why should we think it’s an important factor more generally? What do we mean by ‘relative importance’ anyhow? Unless we tackle these higher-level questions, there will be no escape from Gould’s endless cycle.


Abbot, Francis Ellingwood. 1866. "Positivism in Theology." Christian Examiner 80: 234-267.

Amundson, Ron. 1994. "Two Concepts of Constraint: Adaptationism and the Challenge from Developmental Biology." Philosophy of Science 61: 556-578.

Barker, Gillian A. 2008. "Biological Levers and Extended Adaptationism." Biology & Philosophy 23: 1-25.

Barker, Gillian, and John Odling-Smee. 2014. "Integrating Ecology and Evolution: Niche Construction and Ecological Engineering." In Entangled Life: Organism and Environment in the Biological and Social Sciences, edited by Gillian Barker, Eric Desjardins and Trevor Pearce, 187-211. Dordrecht: Springer.

Chambers, Robert. 1844. Vestiges of the Natural History of Creation. London: John Churchill.

Currie, Adrian Mitchell. 2014. "Venomous Dinosaurs and Rear-Fanged Snakes: Homology and Homoplasy Characterized." Erkenntnis 79: 701-727.

Erwin, Douglas H. 2008. "Macroevolution of Ecosystem Engineering, Niche Construction and Diversity." Trends in Ecology & Evolution 23: 304-310.

Godfrey-Smith, Peter. 1996. Complexity and the Function of Mind in Nature. Cambridge: Cambridge University Press.

Gould, Stephen Jay. 1977. "Eternal Metaphors of Palaeontology." In Patterns of Evolution as Illustrated by the Fossil Record, edited by A. Hallam, 1-26. Amsterdam: Elsevier.

James, William. 1904. "The Chicago School." Psychological Bulletin 1: 1-5.

Laland, K.N., and K. Sterelny. 2006. "Seven Reasons (not) to Neglect Niche Construction." Evolution 60: 1751-1762.

Lewes, George Henry. 1851. "Lyell and Owen on Development." The Leader 2: 996-997.

Lyell, Charles. 1830. Principles of Geology, Being an Attempt to Explain the Former Changes of the Earth’s Surface, by Reference to Causes now in Operation. Vol. 1. London: John Murray.

Ospovat, Dov. 1977. "Lyell's Theory of Climate." Journal of the History of Biology 10: 317-339.

Pearce, Trevor. 2010. "From ‘Circumstances’ to ‘Environment’: Herbert Spencer and the Origins of the Idea of Organism-Environment Interaction." Studies in History and Philosophy of Biological and Biomedical Sciences 41: 241-252.

———. 2011a. "Ecosystem Engineering, Experiment, and Evolution." Biology & Philosophy 26: 793-812.

———. 2011b. "Evolution and Constraints on Variation: Variant Specification and Range of Assessment." Philosophy of Science 78: 739-751.

———. 2012. "Convergence and Parallelism in Evolution: A Neo-Gouldian Account." British Journal for the Philosophy of Science 63: 429-448.

———. 2014a. "The Dialectical Biologist, circa 1890: John Dewey and the Oxford Hegelians." Journal of the History of Philosophy 52: 747-778.

———. 2014b. "The Origins and Development of the Idea of Organism-Environment Interaction." In Entangled Life: Organism and Environment in the Biological and Social Sciences, edited by Gillian Barker, Eric Desjardins and Trevor Pearce, 13-32. Dordrecht: Springer.

Pigliucci, Massimo, and Gerd Müller, eds. 2010. Evolution—The Extended Synthesis. Cambridge: MIT Press.

Powell, Russell. 2012. "Convergent Evolution and the Limits of Natural Selection." European Journal for the Philosophy of Science 2: 355-373.

Spencer, Herbert. 1855. The Principles of Psychology. London: Longman, Brown, Green, and Longmans.


Trevor Pearce is Assistant Professor of Philosophy at the University of North Carolina at Charlotte. He is currently writing a book, tentatively titled Pragmatism's Evolution: Organism and Environment in American Philosophy, that explores the complicated interactions between biology and philosophy in America around 1900. He co-edited the collection Entangled Life: Organism and Environment in the Biological and Social Sciences (Springer, 2014), and has written essays on a variety of topics in the history and philosophy of biology: organism-environment interaction, ecosystem engineering, constraints in evolution, evolutionary convergence, and the economy of nature.