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Darwin’s Use of Natural Selection, and Metaphors in Science

From its initial publication on November 24th, 1859, Charles Darwin’s On the Origin of Species revolutionized the scientific field through its presentation of evolutionary theory as the biological process capable of accounting for the diversity of life observed in the world.  And the key means by which Darwin proposed evolution to be possible was a mechanism he called natural selection.

From the start, controversy arose against Darwin’s strictly naturalistic explanation for the emergence of new species, and opposition formed swiftly to denounce evolution by natural selection as an insufficient theory that is unscientific in its analysis.  Most of the early opposition was religious in nature, but a more legitimate note of dissent came from Darwin’s own colleague Alfred Russel Wallace, who criticized Darwin’s choice of diction in referring to the evolutionary process by the term natural selection as misleading to the general public, because it needlessly implied a selector in the process.  Darwin countered Wallace’s objection by making the case that, for explanatory purposes, natural selection served as a sufficient term as it gives people a descriptive (albeit metaphorical) idea of how the wholly naturalistic phenomenon operates in comparison to the widely familiar practice of artificial selection.

Wallace himself was a proponent of evolution (often referred to as its co-discoverer along with Darwin), and was by no means opposed to the idea of natural selection.  He simply preferred the phrase “survival of the fittest” as a much better alternate to natural selection, arguing:

Natural Selection is, when understood, so necessary and self-evident a principle, that it is a pity it should be in any way obscured; and it therefore seems to me that the free use of “survival of the fittest,” which is a compact and accurate definition of it, would tend much to its being more widely accepted, and prevent it being so much misrepresented and misunderstood.[1]

Wallace thought that among the scientists in the field, who understood their work, the use of natural selection was not an issue, but among those who did not understand evolution and its process, the metaphor would fail to convey Darwin’s true meaning.  Undoubtedly aware of the attacks his and Darwin’s theory was already being subjected to, Wallace must have been worried that confusing people about the function of natural selection with metaphorical language would only serve to move skeptical minds further away from embracing evolutionary theory.

Darwin responded by agreeing that natural selection can be misleading to some, and even decided to incorporate “survival of the fittest” alongside natural selection as a compromise to Wallace in subsequent editions of On the Origin of Species.  But Darwin also commented how through the continued use of natural selection, his intended meaning will become more widespread, and weaken the sort of objections Wallace made.[2]  Despite these concessions on the issue, Darwin remained largely dismissive of Wallace’s concern, even bluntly responding that Wallace overstated the case for the opposition, and implied that certain individuals will misinterpret any term simply because they are too keen on scrutinizing over matters that are trivial to the average person.[2]

Darwin introduced the concept of descent through modification (i.e. evolution) in Chapter I of On the Origin of Species by drawing parallels to the artificial selection observed in animal domestication[3], something most of his readers would have been familiar with at the time.  He does this as a means of easing his audience into his argument in Chapter IV, where he finally makes his case for natural selection.  The confusion Wallace referred to can be argued here by Darwin’s parallel between artificial and natural selection, and his stating how, “this preservations of favourable variations and the rejection of injurious variation, I call Natural Selection,”[4] because it indicates the presence of intelligent oversight (as is the case for artificial selection), when in reality no such implication need be made for the process to function.  Though in his exchange with Wallace, Darwin appeared to be shrugging the matter off as a nonissue, he nevertheless thought it important to both defend his use of natural selection, and clear up any confusion about his intent in later editions of the book:  “It is difficult to avoid personifying the word Nature; but I mean by Nature, only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us. With a little familiarity such superficial objections will be forgotten.”[5]  Thereby reiterating his confidence that by continually familiarizing the public with his true intended meaning for natural selection, the term can be salvaged and the misguided dissent will disappear.

Charles Darwin insisted that metaphorical terms are needed in science for the sake of expressing an idea, and that it is the general descriptive quality that ought to be focused on by readers, not so much the personification of abstract concepts.  For example, when one says that particles are physically attracted to one another, few actual think there is some sort of conscious intimacy taking place between the consciousness-devoid matter.  Same goes with the description that gravity pushes down on a table, in that nobody would claim that the result caused by the force is driven by a self-awareness to hold on to the object.  In the case of natural selection, while in a literal sense a misnomer, it is nevertheless an apt description of the mechanism taking place.

Despite what is often asserted within anti-Darwinian circles, evolution by natural selection is actually not a completely random phenomenon, in that there does occur a mode of selection.  To explain it simply:  Different variants exist among and within different species, exhibiting different traits; some of them will be better adapted to a given environment, thus they will better survive in said environment, leaving more descendants with the same beneficial traits than the less adapted species.  It is blind, unguided, and in the long-run goalless, but also not really random, in that nature itself non-randomly provides the setting in which the various random traits will either flourish or flounder.  Thus, although the selector is an unintelligent and unaware agent, it is a selector nonetheless; a natural selector.  Meaning that Darwin’s use of natural selection as a metaphorical expression to describe the mechanism of evolutionary theory is a fitting one, and an entirely justifiable one.

Natural selection, as a term, is metaphorical only in the broad sense, but very descriptive in light of the proper understanding of the science involved in its function.  Darwin was right to point out that, given enough promotion, a phrase will begin to take on the definition popularly assigned to it even among the most stubborn minds.  Originally, the Big Bang was coined as a dismissive mockery of the theory, and is neither accurate not descriptive, but it has such wide use that objections have been thoroughly forgotten, and nobody emphasizes its metaphorical implications.  This leads into the main point, and it is one that Darwin himself indirectly made to Wallace, how for those who are opposed to the implications of evolution no term or explanation will be justifiable, and misconstruing natural selection is a means by which to either conform the concept to their personal liking or discredit it as insufficient.  The same would happen with “survival of the fittest,” or any other alternative phrase that could be proposed.  And it is through the merit of its work that science is judged, not by its ability to accommodate to the ignorance of its detractors.

 

[1] Francis Darwin and A. C. Seward, eds., More Letters of Charles Darwin:  A record of his work in a series of hitherto unpublished letters (London: John Murray, 1903. Vol. 1.), 270.

[2] Francis Darwin and A. C. Seward, eds., More Letters of Charles Darwin:  A record of his work in a series of hitherto unpublished letters (London: John Murray, 1903. Vol. 1), 272.

[3] Darwin, Charles. The Origin of Species ed. James Secord (Oxford: University Press, 2008), 111.

[4] Darwin, Origin of Species, 141.

[5] Darwin, Charles. The Origin of Species, 6th edition (London: John Murray, 1872), 63.

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Hypotheses non fingo, hypothesis non egeo

“A god without dominion providence, and final causes, is nothing else but Fate and Nature.”[1]

Much of the 18th Century Enlightenment can be explained by the approach framed by one man, Sir Isaac Newton, whose emphasis on analysis and observation served as a model for future scientific generations that sought to follow in his footsteps.  But unlike many of the minds that would succeed him, Newton was a devout believer in divine authority, and saw no reason to dissever the word of the Almighty from the laws of Nature—ultimately deducing them to be one and the same.  Although Newton saw no contradictions in appealing to the supernatural as a valid explanation to matters of scientific inquiry, the empiricism of 18th Century France began to direct science further away towards the realm of strict materialist rationalism.  In the late 18th and early 19th Century, mathematician Pierre-Simon Laplace, admiringly called the Newton of France by contemporaries, was the embodiment of the latter sentiment; working relentlessly to understand and solve the minute details Newton had either overlooked or deemed divinely guided.

Laplace’s work was an ambitious attempt to account for how the solar system works; hence appealing to agents beyond the scope of man’s intellect (meaning his intellect) was not just unsatisfactory, but downright unacceptable.  This naturalistic mindset is best illustrated by the oft repeated exchange he had with Napoleon Bonaparte in 1802: the story goes how upon receiving one of Laplace’s latest manuscripts aiming to systematically account for the functions of the universe, Napoleon turned to the mathematician and asked Laplace why it is that he had written an entire book about the intricate details of the universe with no mention of God in it, to which Laplace answered bluntly, “I have no need of that hypothesis.”[2]  This exchange reveals much about Laplace’s personal weltanschauung concerning the utility of accepting metaphysical analyses.  Ironically, it also further imitates Newton’s legacy by setting a precedent; a standard of doing science that influenced the subsequent generation of European thinkers to come.  Except in the model set by Pierre Simon Laplace, theology and deities could have no role in scientific reality.

In Laplace’s quest to decipher the mathematical properties of the universe, he committed himself wholeheartedly to Newton’s theory of universal gravitation as proposed by the English natural philosopher in his Principia Mathematica.  To Laplace, if there existed a concept that could bring all the functions known to science at the time together it was gravity as described by Newton, and it is of importance to note that when it comes to his mathematical calculations, Laplace is a strict Newtonian.  And the system he deduced to be at work from all this was self-operating, and firmly set, rendering appeals to the supernatural redundant in the highest degree.  Thus, Laplace must have been baffled to know that Newton himself was not as strict a Newtonian as Laplace was, because despite laying out a mechanical approach to understanding the cosmos, he still left room for a supernatural agent—i.e. God—to not just set the mechanism in motion, but also tinker with it as the he saw necessary.[3]

One particular case that Newton noted as evidence of occasional divine intervention in the solar system concerned the gravitational interactions of Saturn and Jupiter, whose strange pattern of accelerating and decelerating as they revolved on their orbits produced certain mathematical irregularities that suggested that the planetary system would become unstable over time.[4]  And it is in this sort of an apparently scientific anomaly that Newton asserted that the hand of God is required to sustain and stabilize the system into order.  Laplace could not accept Newton’s conclusion on this problem, and would spent a significant amount of his professional career providing mathematical evidence as to why Newton was wrong to presuppose divine assistance when his own work points to quite the opposite.

Laplace’s earliest attempt to answer the dilemma posed by the Jupiter/Saturn problem, presented in 1773, resulted in his conclusion that the gravitational attraction mutually exerted by planets was negligible, even nil.[5]  However, he did not find this answer satisfactory, and presented another—what he considered more thorough—explanation a decade later to the French Academy of Sciences, in his famous 1785 paper, Memoire sur les inegalites seculaires des planets et satellites.  Here, Laplace approached the Jupiter/Saturn problem by stating that the discrepancies observed in regard to planetary orbits, and how their motions affected the relative stability of the solar system, can be accounted for mathematically because they do in fact regularly reverse themselves when one maps out their motions on a long-term basis, proving the system to be stable after all.[6]  Though we know today that Laplace’s calculations exaggerated the stability of the solar system (there exists quite a bit of irregularity in the cosmos), his unyielding pursuit of a naturalistic explanation to the problem gives a lot of insight into his staunch determinism, where every event is caused by a verifiably preceding event and will result in a predictable consequent, excluding supernaturalism from its framework.  It is the principle around which Laplace would strive to orient his scientific career, and establish his personal ideals under.

By 1802, the year of his famous encounter with the First Consul of France, Laplace was 53 years old and highly regarded as one of the greatest living mathematicians in France.  He had survived the turmoil of the French Revolution that had taken the lives of so many of his colleagues by always maneuvering himself in the right political circles, but never associating himself to any one group closely enough to suffer their eventual downfalls.  Throughout the mid-late 1790s, Laplace began to have an increasing presence within political circles, starting with a string of leading positions in the founding of the Bureau des Longitudes (created in 1795 for the advancement of astronomy in the French Republic) and the Institute National des Sciences et des Arts (serving as a successor to the defunct Academy of Sciences, organized for the purpose of utilizing science for the benefit of the new Republic).  Laplace’s role as a leading figure in France’s scientific community made his inclusion in these activities a necessity for the state, and brought him closer into the spotlight of the national scene, meaning closer to the man who was accumulating more power within France, Napoleon Bonaparte—the recipient of Laplace’s blunt statement about God’s absence in the workings of the universe.

A lot of Laplace’s influence in the early 19th Century can be attributed to his personal relationship with General Bonaparte, who upon seizing power in 1799 appointed the mathematician as his minister of the interior. This gave Laplace his first taste of true political power (even though Napoleon soon regretted the decision, as the ministerial post proved to be a poor match for the meticulous scientists).  Later in life, Laplace would comment how when it comes to politically ambitious individuals, “rather than crave their lot, I am more likely to pity them.”[7]  Though he relieved Laplace as minister of the interior soon after appointing him, Napoleon ensured Laplace’s position in a more politically ceremonial role in the newly forged Senate in late 1799, naming him secretary of the Senate in 1800, and eventually chancellor of the Senate in 1803.  Laplace used his sway in politics to benefit science and its practitioners, and indeed it appears as if his primary actions involved the advancement of scientific institutes,[8] earning him much praise from the rest of the academic world.[9]  This is very much in contrast to his idol Newton, who mostly shied away from the public eye all through his life.  Also unlike Newton, Laplace did not care to allow potential successors to arbitrarily follow in his footsteps, but sought to carefully select the best and the brightest to be included in his scientific projects; founding an elite social club for budding scientists called the Societe d’Arcueil in 1806 to promote what is referred to today as the Laplacian program.  The Laplacian program of precise experimentation and consistent mathematical theory set-up by the Societe would influence the direction of French scientific learning for nearly two decades, only fading out close to Laplace’s death in the 1820s as the group virtually imploded in its overreaching quest to account for everything in existence.

The standard by which Laplace was eager to frame and promote the study of science was a clear reflection of his own ambitious attempt to explain the nature of the various components, and how they operate to make up all the matter surrounding life and the universe.[10]  Thus, the only logically consistent position this sort of mindset could lead to for someone like Laplace is that as far as he is concerned the laws of nature are static, leaving no room for miracles of any sort, chiding past and contemporary scientists for straying away from what he thought ought to have been their better judgment and slipping into the realm of unfounded superstition.[11]

Laplace clearly idolized Newton, and was thoroughly committed to Newton’s theory of gravity as a universal truth that gives a sufficient account of how the solar system functions.  But he never shared Newton’s strong religious convictions, and never understood how a mind so great as to practically invent physics, did not reach the same metaphysical conclusions Laplace himself had done through his own work on calculating the cosmos.[12]  Whereas Newton asserted that the observation of peculiar patterns in the motion of planets and other celestial bodies was a sign for the occasional suspension of natural laws to validate the necessity of a Supreme Being’s oversight in the ultimate structure of the universe, Laplace saw these same peculiarities as natural consequences of these very same laws Newton was willing to suspend, seeing no function for God to play in what he considered to be a wholly deterministic system.

Laplace was a young man he was dubbed the “Newton of France,” but, unfortunately, Newton had not left a lot of unexplored domains for his intellectual heir to discover, leaving the ambitious Frenchman to be content with exploring the areas where his forbearer had been negligent: working out the minuscule details that combine to make up the grand picture.  To a devout believer such as Isaac Newton, the presence of God within our reality is the grandest of all explanations; to a man like Pierre-Simon Laplace, focusing on the minute workings of the larger framework, the concept of God can never reach more than a hypothesis.  A hypothesis that might be satisfactory to the philosophically inclined, but to Laplace, the empiricist, the scientist, it is a hypothesis for which there is no need.

[1] Newton, Isaac.  1687.  Principia Mathematica. “Rules of Reasoning in Philosophy, Rule IV”.

[2] Hahn, Roger. The Analytic Spirit, ed. Harry Wolf. “Laplace and the Vanishing Role of God in the Physical Universe” (Ithaca, 1981), p. 85.

[3] Newton, Isaac. 1776.  Principia. General Scholium.

[4] Gillispie, Charles Couston.  Pierre-Simon Laplace: A Life in Exact Science (New Jersey: Princeton University Press), 1997, p. 47.

[5] Hahn, Roger.  Pierre Simon Laplace: A Determined Scientist (Cambridge, Massachusetts: Harvard University Press), 2005, p. 78.

[6] Laplace, Pierre Simon.  1785.  “Memoire sur les inegalites seculaires des planets et des satellites.”  A detailed account that helps to clarify some of the technical jargon of Laplace’s conclusions can be found in Chapter 16 of Gillispie’s book, titled “Planetary Astronomy”, p. 124-145.

[7] Hahn 2005, p. 130.

[8] Hahn 2005, p. 133-134.

[9] Monatliche Corrospondenz zur Beforderung der Erd-und Himmels-Kunde 6, 1802, p. 272-278

[10] Laplace, Pierre-Simon. 1801. Mecanique Celeste, p. 121-122.   

[11] Moniteur Universal. 28 January 1795, p. 530.

[12] Hahn 2005, p. 201.