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Toni Vogel Carey on discovering interconnections.

Consilience’ is an important term in philosophy of science, one with a distinguished history; yet you may never have heard of it. The late Stephen Jay Gould bemoaned the fact that this “lovely and deserving term… never caught on in the ‘natural selection’ of English vocabulary” (The Hedgehog, the Fox, and the Magister’s Pox, p.192, 2003). Indeed he thought he was the only recent evolutionary biologist to use it, until he found his Harvard colleague E.O. Wilson using it with a different and conflicting meaning: but about that, more later.


It is not just the term ‘consilience’ that is a well-kept secret, but the idea behind it: that scientific evidence is particularly powerful when found in places we are least likely to look. Here is the astronomer John Herschel in his Preliminary Discourse on the Study of Natural Philosophy (1830):

“The surest and best characteristic of a well-founded and extensive induction… is when verifications of it spring up, as it were, spontaneously, into notice, from quarters where they might be least expected, or even among instances of that very kind which were at first considered hostile to them. Evidence of this kind is irresistible, and compels assent with a weight which scarcely any other possesses.” (Sec. 180)

Herschel may have been the first to describe this phenomenon in print, but according to Larry Laudan (Monist, 1971, p.381), William Whewell sketched the idea in an unpublished manuscript during the 1820s, and even made it one of his ‘Rules of Philosophizing’. Thus Herschel and Whewell, friends from their Cambridge undergraduate days, came to this idea concurrently, if not collaboratively, but it was Whewell, an inveterate coiner of terms, who dubbed it a ‘consilience of inductions’ – from the Latin salire (to jump), and con (together). That was in 1840, in his Philosophy of the Inductive Sciences. By 1843 J.S. Mill was using the term in his System of Logic.

“The evidence of history and that of human nature combine, by a striking instance of consilience, to show that… the relative weakness of this principle among other sociological agents… is the main determining cause of the social progress” (VI.x.7.)

Appearing as they did in such short succession, these three works by Herschel, Whewell and Mill established philosophy of science as a field in its own right.

Whewell’s favorite example of consilience was Newton’s theory of universal gravitation, because it brought together Kepler’s three laws, which until then had not been seen as connected (Gould, HFMP, p.21). And as Laura Snyder says in The Philosophical Breakfast Club (2011), Newton found that different kinds of phenomena all ‘leapt to’ the inverse-square law of attraction.

Even before Newton’s Principia (1687), Descartes asserted in his Principles of Philosophy (III.xlii, 1644) that we do not know our theories are correct unless “we see that we can explain in terms of them, not merely the effects we had originally in mind, but also other phenomena of which we did not previously think.” Before that, Galileo (1564-1642) put forward the idea of ‘demonstrative advance’: that “the inherent uncertainty of any assumption is reduced when conclusions derived from it point to other phenomena that were unknown, or not considered, when it was adopted.” (Drake, Reexamining Galileo’s Dialogue, 1986.)

Thus consilience was in the air from the birth of modern science, and it was taken up by Adam Smith in the eighteenth century before Herschel and Whewell came along. In a treatise on scientific method, The Principles which Lead and Direct Philosophical Enquiry, Illustrated by the History of Astronomy, Smith touted Newtonian gravitation as the pinnacle of science, not only because the parts of that system, as he said, “are more strictly connected together than those of any other philosophical hypothesis” but also because these parts had formerly seemed just “disjointed and discordant phaenomena.” I mention this rather obscure treatise because we know that Whewell was acquainted with it, confiding to a friend in 1822 that he considered writing “something like Smith’s History of Astronomy, but with more historical facts.”

The Smith-Whewell connection is significant too because these two figures stand out in the history of philosophy of science for placing more importance on internal connectivity (coherence) than on conformity to fact (correspondence). Not until Karl Popper, I think, do we find another philosopher so firmly downplaying verification and insisting that theories predict phenomena which have not so far been observed. In Science and Hypothesis (1981), Laudan calls this a ‘reformulation’ of consilience, and says that Popper “required a ‘good’ hypothesis to do precisely what Whewell expected it to do.”

Natural Selection

It seems strange that so few have made use of the criterion of consilience; and even fewer, of course, have done so because of its association with Herschel and Whewell. Charles Darwin, however, is one who did.

In his Autobiography (p.67ff), Darwin wrote that reading Herschel’s Preliminary Discourse as a Cambridge undergraduate had instilled in him “a burning zeal to add even the most humble contribution to the noble structure of Natural Science.” And there was no one whose good opinion he craved more for his theory of descent than Herschel’s. He worried that his theory would be considered “grievously hypothetical… my commonest error being probably induction from too few facts” (More Letters, p.126). But natural selection cannot be based on induction from facts, at least not in anything like the conventional Baconian sense, since it cannot be observed, but only inferred. We think of Darwin as a great observer, and of course he was. But the process of natural selection is invisible – a prime example, in fact, of what Adam Smith in his economic writings called ‘invisible hand’ connectivity. Gould actually considered Darwin’s and Smith’s principles “isomorphic – that is, structurally similar point for point, even though the subject matter differs” (‘Darwin and Paley Meet the Invisible Hand’ in Natural History 99, Nov. 1990, p.14). (One thing Gould did not have in mind here, I should add, is Social Darwinism, which was the brainchild of neither Smith nor Darwin, but of Herbert Spencer.) Like Herschel, Whewell and nearly every other scientist up to that time, Darwin paid lip service to Francis Bacon by picturing and/or quoting him at the opening of a book. But Bacon is never mentioned in the text of the Origin of Species, which rests on the subtler, more sophisticated method of consilience. Darwin wrote to Asa Gray in 1859 (Correspondence 7, p.369):

“I fully admit that there are very many difficulties not satisfactorily explained by my theory of descent with modification, but I cannot possibly believe that a false theory would explain so many classes of facts as I think it certainly does explain. On these grounds I drop my anchor, and believe that the difficulties will slowly disappear.”

He wrote something similar in a letter to Herschel himself in 1861 (Correspondence 9: pp.135-6), and starting in 1860 he incorporated the point in all subsequent editions of the Origin (cf Prometheus edition, p.401). Darwin compared his theory to Newton’s, not to Bacon’s. To say that three species of rhinoceros were separately created, he argued, would be like saying that the fall of a stone bears no relation to the orbital movement of the planets, contrary to Newton’s crowning achievement.

Darwin considered natural selection “one long argument” for descent from a single species, or at most only a few (Origin, p.404). So his theory fits hand-in-glove with Newton’s first Rule of Reasoning, that “more is in vain when less will serve; for Nature is pleased with simplicity,” and with Whewell’s assertion that consilience amounts to “a constant Convergence… towards Simplicity and Unity.” (Novum Organum Renovatum, 1858.)

More recently, Gould called consilience Darwin’s “primary method” and the Origin of Species “a brief for evolution by consilience.” In fact he called the Origin “the most instructive case for consilience in all of science” (HFMP, p.211-12).


In 1998 E.O. Wilson revived the term with a flourish as the title of his book Consilience, and proclaimed “trust in consilience” to be nothing less than “the foundation of the natural sciences” (p.10). There is a big difference, however, between Wilson’s consilience and Whewell’s. Wilson advocates a “deliberate, systematic linkage… across the disciplines” (p.27), whereas what Herschel and Whewell had in mind was the unexpected, serendipitous discovery of interconnections. It may create more confusion than clarity, then, to call Whewell’s concept and Wilson’s by the same name.

Discovery without surprise is almost a contradiction in terms. Indeed the Nobel biologist Francois Jacob said, “you can almost measure the significance of a scientific study by the intensity of the surprise.” (Of Flies, Mice, and Men, p.13, 1998) Another Nobel biologist, Francis Crick, remarked in What Mad Pursuit (1988) that many “previously puzzling facts” unexpectedly turn out to be “neatly explained” by the double-helix structure of DNA that he discovered with James Watson. It is doubtful that Crick had heard of consilience, but he was making use of the idea nonetheless.

The other side of the ‘surprise’ coin is that chance favors the prepared mind. And that creates another kind of surprise – the obviousness, in retrospect, of many discoveries. Thomas Huxley’s reaction on first hearing of natural selection was: “How extremely stupid not to have thought of that!” Michael Polanyi wrote in Science, Faith and Society (pp.34-5) of “a presence staring us in the face, waiting until we open our eyes,” and described discovery as “a process of spontaneous mental reorganization uncontrolled by conscious effort.” Herschel’s description of consilience also uses the term ‘spontaneous’. And Scottish Enlightenment scholars make much of the notion of ‘spontaneous order’. Here is David Hume, for instance, in the Dialogues of Natural Religion, Part VII (1779):

“A tree bestows order and organization on that tree which springs from it, without knowing the order: an animal, in the same manner, on its offspring: a bird, on its nest. And instances of this kind are even more frequent in the world, than those of order which arise from reason and contrivance.”

Adam Ferguson’s Essay on the History of Civil Society (1767) extended the idea of spontaneous order to societal ‘establishments’ (p.182):

“The artifices of the beaver, the ant, and the bee are ascribed to the wisdom of nature. Those of polished nations are ascribed to themselves, and are supposed to indicate a capacity superior to that of rude minds. But the establishments of men, like those of every animal, are suggested by nature, and are the result of instinct, directed by the variety of situations in which mankind are placed. Those establishments arose from successive improvements… made without any sense of their general effect.”

Natural selection, of course, functions as a source of spontaneous order, as does Smith’s invisible hand. But we don’t hear much about spontaneous order in most quarters, in part no doubt because ever since Descartes we have exalted reason and denigrated sub-rational faculties like sentiment and intuition, which helps to explain why we hear so little about the Scottish Enlightenment philosophers. Wilson’s Consilience is a case in point; he devotes an entire chapter to the Enlightenment, but accords Hume, Smith and Ferguson just a sentence (on p.275).

An unintended consequence of this bias toward Reason (with a capital R) is that we associate unintended consequences with unwanted surprises. The Scottish thinkers were aware that there are invisible ‘backhands’ as well as ‘forehands’; but their emphasis was on the upside of surprises, believing as they did that the very foundations of society – language and law, money and property – arise by the ‘wisdom of nature’ without the help of conscious human design.

Friedrich Hayek (who dedicated his Studies in Philosophy, Politics and Economics to Popper) and Popper (who dedicated his Conjectures and Refutations to Hayek) were among the few twentieth-century thinkers to embrace this Scottish Enlightenment idea. Popper even went so far as to claim that the “main task” (his italics) of the ‘theoretical social sciences’ is to study “the unintended social repercussions of intentional human actions,” and “to analyse in this way the existence and the functioning of institutions (such as police forces or insurance companies or schools or governments) and of social collectives (such as states or nations or classes).” (Conjectures, p.125) Auguste Comte, who coined the term ‘sociology’ in 1838, is usually called the father of the field; but the real father of this baby was probably Adam Ferguson in 1767 in his Essay on the History of Civil Society.

Gould vs. Wilson

Gould is known to most readers for short essays originally published over thirty years in Natural History magazine. But in The Hedgehog, the Fox, and the Magister’s Pox, one of his last books, he wrote a seventy-page-long critique of Wilson’s Consilience. Gould particularly attacked what Wilson called his ‘central idea’, that “all tangible phenomena, from the birth of stars to the workings of social institutions, are based on material processes that are ultimately reducible, however long and tortuous the sequences, to the laws of physics” (p.193). While acknowledging that reduction is “a powerful method that should be used whenever appropriate” (p.201), Gould argued (p.203) that Wilson extends this method in a way that violates both Whewell’s notion of consilience and his own.

To be sure, in some ways Wilson’s idea of consilience recalls Whewell’s. Both, for instance, clearly tend toward “simplicity and unity” in explanations; and Whewell too considered physics the premier science. As Secretary of the British Association in 1833, he put in place a hierarchy of the sciences that to some extent still holds sway, with physics and astronomy on the top rung of the ladder, and then relatively primitive fields like statistics on the bottom rung. Whewell was not a reductionist, though; he believed that all sciences should aspire to be as mathematical and Newtonian as possible because this represents the pinnacle of scientific achievement, not its lowest common denominator. Much has changed, though, since Whewell’s time. He could not have foreseen that biology, which is full of what Gould calls “slop” and “redundancy”, would one day rival physics for pride of place. Economics was still a science for which Whewell considered simple Baconian inductivism entirely appropriate, whereas today it is so pristinely mathematical that people question its relevance to the real world.

Gould’s quarrel with Wilson resembles a split within evolutionary epistemology. One side emphasizes the emergence of epistemological mechanisms (EEM) from biological ones – of memes from genes. The other side emphasizes the emergence of epistemological theories (EET), the developing content of memes from other memes. EET cannot account for the biological origin of our concepts; but EEM cannot account for the evolution, say, from Kepler’s theory to Newton’s, or from Newton’s to Einstein’s.

Gould’s argument, in effect, is that Wilson makes too much of EEM and not enough of EET. As he says, Wilson “seems to feel that if he can specify the historical origin of ethics empirically [which Gould regards as possible] he has solved the basic problem of morality and established a basis for the reduction of ethical philosophy to the natural sciences within his grand chain of consilience” (p.246). Indeed, Wilson asserts that on an empiricist worldview, “ought is just shorthand for one kind of factual statement.” (Consilience, p.274.) Gould objects to his fudging Hume’s famous is/ought distinction in this way. He points to the phenomena of emergence, which involves laws arising from interactions among constituent parts that are not explainable in terms of the parts alone; and of contingency, “the growing importance of unique historical ‘accidents’ that cannot, in principle, be predicted” – although they can be explained after the fact.

Like Gould, Wilson is a world-class biological scientist and philosopher, and I find it odd that he would consider what by now is old-hat reduction to physics “the cutting edge of science” (quoted in HFMP, p.191). But that aside, I think Wilson’s consilience fails because any view of science that disregards the element of surprise will fail. In all fields there are ‘Aha!’ discoveries that turn “a previously chaotic system of unconnected facts” into a “highly salutary simplicity.” I quote Gould here, but he sounds just like Herschel and Whewell and Adam Smith, as well as Descartes and Galileo, not to mention Newton with his proverbial apple. There is a new book by Edward Slingerland and Mark Collard, Creating Consilience: Integrating the Sciences and the Humanities (Oxford, 2012) that I have not seen, but their title suggests that they follow Wilson’s lead. I hope this does not signal a trend, though, for like Gould, I find Herschel and Whewell’s consilience more interesting and insightful than Wilson’s.

© Dr Toni Vogel Carey 2013

Toni Vogel Carey is an independent scholar who writes about philosophy and the history of ideas. She is a regular contributor to Philosophy Now, and a member of its board of U.S. advisors.

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