On the Origin of Species and the Limits of Science
On the Origin of Species and the Limits of Science
Abstract and Keywords
Currently the United States is home to a small but mobilized grassroots effort to have the model of intelligent design (ID) integrated into public school science curricula. What might seem strange is that many of the leading advocates for ID are well aware that by most current definitions, ID does not qualify as science. ID is not the first theory to challenge the scientific community to rethink the limits of the scientific method. In some cases, revolutionary discoveries have required scientists to discard everything they previously thought about a subject or its proper method of study. When Charles Darwin first published On the Origin of Species, many of his critics seized on his methods just as fiercely as they did on his conclusions. This essay compares ID with natural selection, a theory that in fact broke new methodological ground in the past, to demonstrate that the exclusion of ID from proper science is due not to some shortsightedness on the part of the scientific community, but to ID's own implicit weaknesses.
Currently the United States is home to a small but mobilized grassroots effort to have the model of intelligent design (ID) integrated into public school science curricula. What might seem strange is that many of the leading advocates for ID are well aware that by most current definitions, ID does not qualify as science (CSC Top Questions). Many ID advocates admit that their methods and conclusions go beyond what are conventionally accepted as the limits of appropriate scientific explanations; but this, they claim, betrays a flaw in our current conceptions of science. Truth, they say, lies beyond the arbitrary rules of scientific orthodoxy, and only by pushing those boundaries can we find the true nature of the universe. Unfortunately for its proponents, ID makes no compelling claims as to why its methods should be admitted into the fold of legitimate science. In this essay, a comparison of ID with natural selection, a theory that in fact broke new methodological ground in the past, will demonstrate that the exclusion of ID from proper science is due not to some shortsightedness on the part of the scientific community, but to ID’s own implicit weaknesses.
ID is not the first theory that has challenged the scientific community to rethink the limits of the scientific method. In some cases, revolutionary discoveries have required scientists to discard everything they previously thought about a subject or its proper method of study. When Charles Darwin first published On the Origin of Species, many of his critics seized on his methods just as fiercely as they did on his conclusions. The resulting debate among the scientific community helped to (p.142) expand the toolbox of scientific investigation. Darwin’s book literally changed what it meant for a theory to be considered scientific (Ellegård 1957). In the case of ID, however, the conflict between theory and scientific norms reflects not a need to expand our definition of science but rather a need to clarify the boundaries of science.
A comparison of the intellectual contexts in which natural selection and modern ID were first proposed makes apparent the important differences in their relationships with contemporary scientific thought. Darwin was an integral part of a wider intellectual movement. Victorian philosophers of science, including William Whewell (1840) and John Stuart Mill (1843), were already arguing for a broader range of acceptable scientific methodologies. Darwin was then an exemplar of how these new methodologies could be used to explore nature. ID advocates, on the other hand, offer no independent justification for an expansion of scientific norms beyond promoting their own arguments. The few attempts that have been made to broaden state science standards to include ID are not reflective of a broader intellectual movement. Instead, they are a type of special pleading designed purely for the purpose of legitimizing ID after the fact. Taken to their logical conclusions, the type of pseudoscientific methods that ID adherents advocate would actually weaken the ability of all scientists to posit any acceptable explanations.
On the Origin of Species and its Intellectual Context
Perhaps appropriately, Charles Darwin’s theory of natural selection did not originate fully formed. The idea that human life may have originated from some earlier ancestral species can be traced all the way back to the Greek philosopher Anaximander in the sixth century BCE. In the late eighteenth and early nineteenth centuries, these notions of transformational biology were even experiencing a mild revival through the works of the French naturalist Jean Baptiste Lamarck and Darwin’s grandfather Erasmus Darwin. What made Charles Darwin’s work controversial was not simply the ideas that he proposed, but how he defended those ideas.
In publishing On the Origin of Species, Charles Darwin not only immersed himself in the scientific debate over life’s history, the pattern of diversification of life after its origin from one or a few original forms. He also was engrossed in the philosophical debate over the limits of science. Prior to the Victorian Age, British (p.143) intellectual tradition dictated that only induction was permissible in scientific explanation. That is, the proper way to understand the world was to examine a full range of particular instances and to extrapolate from these particulars to a general law. Scientific deduction, the formulation of general laws that are then verified through observation, was anathema to most British scientists, who viewed it either as a throwback to the benighted times of Aristotle or as the type of frivolous speculation more typical of French intellectualism (Ellegård 1957).
At the beginning of the nineteenth century, proper British science followed a very rigid methodology. In fact, the scientific method was a point of national pride with two archetypical English heroes. Francis Bacon, the canon claimed, brought the scientific method to a state of maturity by shaking off the Aristotelian commitment to deduction from universal principles. And through his strict adherence to the Baconian method, Sir Isaac Newton, the second great figure of English science, unlocked the secrets of celestial motion.
In the Victorian historiography of science, Francis Bacon was the great emancipator. Aristotle may have begun Western scientific inquiry, but his adherence to deduction from general axioms had severely retarded its progress for centuries. Bacon was among the first to point out the effect that human prejudice and expectation could have on science. In the Novum Organum Bacon writes, “The idols and false notions which have already preoccupied the human understanding, and are deeply rooted in it…will again meet and trouble us in the instauration of the sciences, unless mankind, when forewarned, guard themselves with all possible care against them” (1620). According to Bacon, human intuition is the weak link in the scientific method. Only through pure and unbiased observation can the true nature of the universe be discovered.
While Bacon describes the philosophical rules for proper science, it is Isaac Newton whose work best exemplifies the use of these rules. In the Principia, Newton explicitly states the rules of inference that he considers permissible in scientific inquiry: “RULE IV: In experimental philosophy we are to look upon propositions collected by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions. This rule we must follow, that the argument of induction may not be evaded by hypotheses” (1687). According to Newton, only directly observable phenomena are permissible in constructing explanations. For Newton, as for Bacon, the task of the scientist is synthesis—to take disparate observations and induce from these particular cases the general workings of the universe.
(p.144) Newton demonstrates the extent of his commitment to induction in an amendment to the third edition of the Principia. In response to critics who challenge him to explain the cause of gravity, Newton (1687) answers with the now-famous phrase, “Hypotheses non fingo” (I make no hypotheses). In claiming unapologetically that he is simply reporting the facts rather than interpreting them, Newton both rebuffs his critics and reaffirms his commitment to contemporary scientific practice. The job of a good Baconian scientist is to induce principles from observations, not to indulge in vain speculation.
Even as late as 1800, the paradigm of science as purely inductive still held firmly, particularly in geology. In 1807 the Geological Society of London held its first meeting and resolved “that there be forthwith instituted a Geological Society for the purpose of making geologists acquainted with each other, of stimulating their zeal, of inducing them to adopt one nomenclature, of facilitating the communications of new facts and of ascertaining what is known in their science and what remains to be discovered” (Geological Society). The society’s founders considered accumulation and communication of facts to be proper goals for the society, but not necessarily the explanation of facts. Surveying the state of geology in the early nineteenth century will illustrate both the origin and the significance of this decision.
Prior to the founding of the Geological Society of London, scientists and philosophers who studied the Earth could be characterized as either cosmogonists or geologists. Cosmogonists represented the vast majority of pre-nineteenth-century contemplators of the Earth. They debated the Earth’s history based primarily on a desire to demonstrate notions that they held a priori. Actual observation was rarely included in their debates, and when it was, it was simply to illustrate a point, not to form the foundations of a theory (Gillespie 1959). The cosmogonist tradition yielded the famous debate between Neptunists and Plutonists on the origin of granite, and included such pre-Victorian luminaries as Thomas Burnet and Comte Georges Louis Leclerc Buffon.
Those thinkers that we might classify as geologists in the modern sense constituted a minority of Earth scholars in pre-Victorian Europe. They were primarily miners, surveyors, and mineralogists, and their knowledge of the Earth was more practical than that of the cosmogonists. It is this minority group that actually founded the Geological Society of London. Their choice of name for the society is particularly telling. Of the original founders of the society, all but one was a mineralogist (miners and surveyors being initially excluded on social grounds). The choice of the name “Geological Society” rather than “Mineralogical Society” (p.145) reflects the founders’ belief that a central clearinghouse for mineralogical knowledge and description is a crucial stepping-stone toward a more general understanding of the Earth as a whole (Rudwick 1959). The cosmogonist).
The initial mission of the Geological Society of London “of facilitating the communications of new facts and of ascertaining what is known” also reflects the founders’ beliefs of what good science entails. The society would maintain a commitment to induction to improve the state of geology. Previous cosmogonist systems of geology would be considered, by comparison, “a species of mental derangement,” according to the premiere edition of Transactions of the Geological Society (Fitton 1811, p. 208). This premiere edition reinforces the society’s philosophical position by quoting from the Novum Organum on its cover (Laudan 1977): “But if any human being earnestly desire to push on to new discoveries instead of just retaining and using the old; to win victories over Nature as a worker rather than over hostile critics as a disputant; to attain, in fact, to clear and demonstrative knowledge instead of attractive and probable theory; we invite him as a true son of Science to join our ranks, if he will, that, without lingering in the forecourts of Nature’s temple, trodden already by the crowd, we may open at last for all the approach to her inner shrine” (Bacon 1620). Even at a time when some of the most important theoretical volumes on the workings of the Earth were being published in Germany and Scotland, the Geological Society of London maintained its anti-theoretical stance (Rudwick 1985). This policy was not merely some curmudgeonly attempt to curtail wild speculation. It was an adherence to a scientific tradition that stretched back for centuries, upheld by Britain’s greatest intellectual heroes.
On the Origin of Species and its Logical Structure
Darwin’s model in On the Origin of Species is as contrary to the inductive tradition as is structurally possible (Hodge 1992). Rather than use individual cases to build up to an overarching conclusion, Darwin begins with his model. He then asks a simple question: If this model is correct, what would we expect the world to look like? Darwin acknowledged in his personal correspondence that this mode of reasoning might be dismissed as a type of “what if ” storytelling, and anathema to many scientists (F. Darwin 1903). However, he was confident that his was the proper form of argument to answer questions in a historical science.
What is perhaps most remarkable about On the Origin of Species, particularly considering its intellectual context, is that it contains no experimentation whatsoever. (p.146) It is an argument. In the first four chapters, Darwin asserts the adequacy of selection to enact changes in the forms of living things and then supports this assertion through myriad lines of observation. Throughout the remainder of the book Darwin refutes potential counterclaims to his hypothesis and discusses its ramifications, but never proposes an experimental test of his model. Darwin was well aware of the unorthodox structure of his argument, but was also confident that it was the most powerful way to address evolutionary questions. In an 1861 letter to the English botanist J. D. Hooker, Darwin says of one of his reviewers, “he is one of the very few who see that the change of species cannot be directly proved and that the doctrine must sink or swim according as it groups and explains phenomena. It is really curious how few judge it in this way, which is clearly the right way” (F. Darwin 1903, p. 184).
As Darwin pointed out, the realization that a deductive approach was the correct approach for the study of evolution was not widespread among his peers. While many of Darwin’s contemporary critics predictably reacted to the perceived theological implications of his work, the deductive roots of his argument often received equal scorn. Scientists, theologians, and even the popular press eagerly pounced on the logical structure of Darwin’s argument as a means to undermine it.
Philosophical objections from the scientific community are probably best exemplified by a review written by Adam Sedgwick. Sedgwick, a past president of the Royal Geological Society, mentored Darwin in geology. As one of the men who helped develop the geologic time scale, Sedgwick intimately knew the directional succession of organisms preserved in the fossil record. Nevertheless, on first reading On the Origin of Species, Sedgwick sent a letter to Darwin in which he wrote, “parts I read with absolute sorrow; because I think them utterly false and grievously mischievous—You have deserted—after a start in that tram-road of all solid physical truth—the true method of induction” (F. Darwin 1903). Sedgwick was no kinder to Darwin’s method in public. In an 1860 letter to the newspaper The Spectator, Sedgwick wrote, “I must in the first place note that Darwin’s theory is not inductive,—not based on a series of acknowledged facts pointing to a general conclusion,—not a proposition evolved out of facts, logically, and of course including them. To use an old figure, I look on the theory as a vast pyramid resting on its apex, and that apex a mathematical point.” Even for an individual trained in geology with a thorough understanding of the fossil record, the deductive nature of Darwin’s model posed an insurmountable roadblock to its acceptance.
It is noteworthy that even those detractors most likely to object to the content and implications of Darwin’s argument focused their critiques on his methods. In (p.147) an 1860 article for The Quarterly Review, Bishop Samuel Wilberforce, one of Darwin’s best-known contemporary religious critics, specifically concentrated on Darwin’s methodological heresies rather than on his ecclesiastical ones. In discussing Darwin’s lack of empirical rigor, Wilberforce wrote, “There are no parts of Mr. Darwin’s ingenious book in which he gives the reins more completely to his fancy than where he deals with the improvement of instinct by his principle of natural selection. We need but instance his assumption, without a fact on which to build it, that the marvelous skill of the honey-bee in constructing its cells is thus obtained” (p. 253). According to Wilberforce’s review, methodological weakness rather than religious objection should have caused Darwin’s contemporaries to question his conclusions. Wilberforce claimed that Darwin’s conclusions should be embraced despite their apparent contradiction of scripture if they were well supported by experimentation:
Our readers will not have failed to notice that we have objected to the views with which we have been dealing solely on scientific grounds. We have done so from our fixed conviction that it is thus that the truth or falsehood of such arguments should be tried. We have no sympathy for those who object to any facts or alleged facts in nature, or to any inference logically deduced from them, because they believe them to contradict what it appears is taught by Revelation. We think that all such objections savour of a timidity which is really inconsistent with a firm and well-instructed faith. (1860, p. 256)
Wilberforce’s sincerity in stating that his objection to Darwin’s ideas was purely methodological must be taken with a grain of salt, however, because later he struggled to squelch them on religious grounds. However, his rhetoric in this review helps to underscore the strength of the methodological objection to Darwin. Wilberforce undoubtedly opposed Darwin’s model on religious grounds. However, clearly he felt that attacking natural selection as a hypothesis that lacked experimental evidence would undermine support for it more effectively.
The fact that the scientific community more readily accepted inductively based hypotheses is well illustrated by comparing the reception of the theory of natural selection with that of the theory of ice ages. In the late 1830s, geologists had begun to question old models regarding the origin of erratic boulders found in the U-shaped valley of the Alps. Previous naturalists had explained the presence of these enormous and anomalous rocks through the actions of oceanic currents, icebergs, and even compressed air in underground caverns.
(p.148) In his 1837 presidential address to the Swiss Society of Natural Sciences at Neuchâtel, the Swiss naturalist Louis Agassiz first proposed glacial ice as a potential source for erratics. His model was met with a mix of skeptical silence and outright hostility. The German naturalist and aristocrat Baron Friedrich W. K. H. Alexander von Humboldt suggested to Agassiz in a letter that by forgetting the entire affair he might “render a greater service to positive geology, than by these general considerations…which, as you will know, convince only those who give them birth” (Hallam 1983, p. 71). Agassiz responded to his critics with the publication of a massive treatise on glaciers, highlighting each of the individual observations that had led him to his conclusions (Agassiz 1840). By the mid-1840s, the glacial origin of erratics had become the consensus view among European geologists. When Agassiz had presented his theory as a theory with supporting evidence, it was scorned. When he presented the theory as data with an inductively drawn conclusion, it was embraced.
While modern readers might think that an argument about induction versus deduction and the relative value of experimentation in science might be a debate purely among an academic elite, this was not necessarily true in Darwin’s time. Even in the popular press, commentary on Darwin’s theory included a critique of method. An 1871 edition of the magazine Punch contained the following poem:
- DARWIN AND PICKWICK
- “Hypotheses non fingo,”
- Sir Isaac Newton said.
- And that was true, by Jingo!
- As proof demonstrated
- But Darwin’s speculation
- Is of another sort;
- ’Tis one which demonstration
- In nowise doth support.
- Time, theory’s dispeller,
- Will out of mind remove it.
- We say, as said old Weller,
- “Prove it. And he can’t prove it.”
The fact that even the editorial humor of the day made reference to Darwin’s method illustrates how important such considerations were in Victorian England. Scientific method was not merely a point of academic debate; it was a point of (p.149) national pride. For his heretical departure from Baconian ideals, Darwin found himself pilloried from all quarters.
Defending Darwin’s Deductions
From the preceding critiques of On the Origin of Species, one might infer that Darwin was a methodological radical—a maverick whose views had no business being accepted into the fold of “good science.” However, by 1859 the traditionalist view of science as a purely inductive enterprise was slowly beginning to change. William Whewell’s The Philosophy of the Inductive Sciences, Founded upon Their History, published in 1840, and John Stuart Mill’s A System of Logic, published in 1843, had begun to question the necessity of pure induction and to support a new role for deduction in the scientific method.
Whewell took particular exception to Newton and his infamous claim “Hypotheses non fingo.” Newton claimed that only those principles induced from direct observation of phenomena had any place in science. Whewell countered this supposition by pointing out that it, in and of itself, is a hypothesis, and a potentially stifling one: “This is, in reality, a superstitious and self-destructive spirit of speculation. Some hypotheses are necessary, in order to connect the facts which are observed, some new principle of unity must be applied to the phenomena, before induction can be attempted” (Whewell 1840). For Whewell, hypotheses and presuppositions were not only necessary to fruitful science; they were inevitable. Only through superimposing some conception upon the facts could induction ever be possible.
If deduction were permitted as a legitimate component of scientific inquiry, then new modes of scientific investigation would become available. Whewell distinguished between two very different ways to do science. The “Colligation of Facts” referred to the Baconian tradition of assembling experimentally derived observations into general laws. The “Consilience of Inductions,” on the other hand, was a more theoretically driven mode of inquiry. According to Whewell, a theory could be derived independent of observation and then verified after the fact. Consilience-driven science allowed for the verification of hypotheses if they consistently and simply explained facts observed independently.
For John Stuart Mill, a hypothesis was more than simply a framework in which to view the facts; it was a guide to test inductions. In fact, Mill was more permissive than Whewell when delineating the range of hypotheses that might be allowable in science, but more restrictive in what he considered a proven hypothesis (Ellegård 1957). (p.150) In discussing the proper method for verifying inductions, Mill wrote, “The hypothesis, by suggesting observations and experiments, puts us on the road to that independent evidence if it be really attainable; and till it be attained, the hypothesis ought only to count for a more or less plausible conjecture. This function, however, of hypotheses, is one which must be reckoned absolutely indispensable in science” (1843, pp. 15–16). Like Whewell, Mill considered hypotheses to be an integral component of the scientific method. Mere reporting of facts does not constitute science. One cannot draw conclusions without a preconceived intellectual framework. In fact, preconceived notions, whether arising from innate qualities of the human mind or unique experiences, make scientific inference possible. Furthermore, such fundamental assumptions also provide the intellectual context for making observations in the first place. They determine which of all possible observations are actually made.
Darwin was well aware that many of his contemporaries would consider a deductively based model to be nonscientific. However, he was also aware of the logical weakness of such objections. In an 1861 letter to the economist Henry Fawcett, Darwin wrote, “About thirty years ago there was much talk that geologists ought only to observe and not to theorise; and I well remember someone saying that at this rate a man might as well go into a gravel-pit and count the pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!” (F. Darwin 1903, p. 195).
In this sentiment, that theories can suggest observations just as well as observations can suggest theories, Darwin echoed John Stuart Mill. The fact that Mill was both aware and supportive of Darwin’s work is evident in an 1861 letter that Fawcett wrote to his friend Darwin: “I was particularly anxious to point out that the method of investigation pursued [in On the Origin of Species] was in every aspect philosophically correct. I was spending an evening last week with my friend Mr. John Stuart Mill, and I am sure you will be pleased to hear from such an authority that he considers that your reasoning throughout is in exact accordance with the strict principles of logic. He also says the method of investigation you have followed is the only one proper to such a subject” (F. Darwin 1903). Clearly delighted with Mill’s approval, Darwin wrote back, “You could not possibly have told me anything which would have given me more satisfaction than what you say about Mr. Mill’s opinion. Until your review appeared I began to think that perhaps I did not understand at all how to reason scientifically” (F. Darwin 1903).
(p.151) In the century and a half since Darwin’s initial publication, his style of deductive argument has been largely accepted as a proper aspect of the scientific method. This is true, at least in part, because Darwin illustrated the power of arguing from a theory. Francis Bacon had redefined the limits of science to exclude deduction in the Novum Organum. Whewell and Mill advanced the limits of science by positing that good science could also include speculation, provided that speculation made testable predictions that could then be verified. Within just a few decades of Bacon’s writing, his model had its hero in Isaac Newton. In 1859, with the publication of On the Origin of Species, Charles Darwin became the Isaac Newton of theoretically driven science.
Intelligent Design and its Logical Structure
Perhaps appropriately, the general model of ID is an old model that originated largely in its present form and has remained mostly unchanged for the past few thousand years. The basic logical structure of the argument goes back to Aristotle, who argued that while all phenomena have causes, and each of these causes has a cause of its own, there cannot be an infinite regress. Eventually you reach an uncaused cause—the prime mobile, or prime mover. The philosopher Thomas Aquinas co-opted this argument into a proof of the existence of God, which was then rephrased by William Paley in the nineteenth century as the well-known “watchmaker” argument from design:
When we come to inspect the watch, we perceive…that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it….the inference we think is inevitable, that the watch must have had a maker—that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use. (Paley 1802)
Modern ID theory is essentially a quasi-secular reparsing of Paley’s argument. Consider the following excerpt from Darwin’s Black Box, by Michael Behe, a book (p.152) widely considered to be the founding document of modern ID. In this passage, Behe makes an argument that the complexity of living things (in this case ciliated bacteria) requires the workings of an intelligent designer: “In summary, as biochemists have begun to examine apparently simple structures like cilia and flagella, they have discovered staggering complexity, with dozens or even hundreds of precisely tailored parts. It is very likely that many of the parts we have not considered here are required for any cilium to function in a cell. As the number of required parts increases, the difficulty of gradually putting the system together skyrockets, and the likelihood of indirect scenarios plummets. Darwin looks more and more forlorn” (1996, p. 73). The arguments are isomorphic; that is, they are structurally identical: Complexity requires planning. Planning requires intelligence. Intelligence requires a designer.
One might rightly wonder whether the inference of design should be considered an induction or a deduction. It is worth noting that both rhetoric and law prohibit ID advocates from answering that question ingenuously. ID advocates claim to infer the presence of a designer through rigorous and unbiased examination of nature—almost the definition of induction. However, their inference is based not on what they find in nature, but on their inability to explain what they find in nature. They are basing a positive claim about the universe (the presence of a designer) on negative evidence: a form of argument that has been discounted since the time of Aristotle.
In actuality, ID is a deduction. ID advocates presuppose the existence of a creative agent and then use that presupposition to explain what they see. Unlike Darwin, however, ID advocates cannot explicitly say that their model is deductive. The principle that Darwin was trying to deductively demonstrate was natural selection, a mechanical process rooted in natural law. ID advocates are presupposing an unknowable and potentially capricious intelligence, almost the very definition of a mythic entity. If ID advocates were to concede that their model is deductive, they would essentially be conceding that it is merely a thinly veiled form of theistic creationism.
When making the legal argument for the inclusion or exclusion of ID from public school curricula, the identity of Behe’s designer is of paramount importance. Is this all-powerful, unknowable designer God or a god? For the purposes of this essay, however, the identity and attributes of the designer are irrelevant. What is important from a methodological standpoint is the empirical claim that the designer’s presence can be inferred at all. This is precisely where Behe and his adherents claim to be breaking new scientific ground. While science traditionally prefers (p.153) naturalistic and mechanical explanations, ID advocates claim that this should be a starting point rather than an absolute rule.
It is axiomatic in science that a good theory suggests its own tests through its predictions. The best theories are those that explicitly forbid certain phenomena to occur. Science is then the process of holding these predictions and prohibitions up to scrutiny. Data that is inconsistent with the theory requires us to modify that theory. This is the principle of falsifiability (Popper 1963).
As an example, one of the reasons that the theory of plate tectonics is considered a good theory is that it makes predictions about where earthquakes should and should not occur. Consider the following hypothesis that one might make based on the theory of plate tectonics: “Earthquakes occur only as the result of motion along plate boundaries.” Every earthquake that occurs in the Aleutian Islands or along the San Andreas Fault adds support to the hypothesis, but no number of them would ever be sufficient to demonstrate conclusively that the hypothesis is correct. Conversely, some earthquakes occur away from plate boundaries, and require additional explanation. These earthquakes, even though they are the minority of earthquakes, refute the hypothesis that earthquakes occur only as the result of motion along plate boundaries. Since these earthquakes are explainable by other means, however, they do not contradict the larger theory of plate tectonics. If geologists were unable to explain these apparently anomalous earthquakes, their occurrence might eventually call the entire theory of plate tectonics into question.
Under modern definitions of science, a theory must be falsifiable to be considered scientific. ID relies on an alternative mode of evidence. The methodology of ID requires verification through an absence of evidence and through falsification of alternatives. If one can demonstrate that a particular scientific model has just one alternative, then one can validate that model by falsifying the alternative.
Unfortunately, this mode of argument is based on invalid claims. First among these is that one can dichotomize the world into diametrically opposed alternatives. Few phenomena exist in nature for which only two possible explanations exist. For example, one cannot prove that the Earth is located at the center of the universe simply by disproving that the moon is located there instead. True dichotomies in nature are typically trivial tautologies: It is either raining outside or it is not. To prove the principle of ID using this mode of argument, one would need to change the structure of the argument from “Biological diversity is a result of either Darwinian selection or intelligent design” to “The universe was either designed (p.154) or it was not.” One would then need systematically to disprove that the universe was not designed. Even if such an effort were possible, what then?
The primary boundary of science that ID advocates claim to be pushing is the premium that science places on naturalistic causes. Currently, for a theory to be considered scientific, it must be reliant on natural causes and the conception of obtainable observations that would refute it must be possible. ID advocates would change this cornerstone of science into a suggestion. Under the logic of ID, naturalistic causes are a good starting point; however, if they are demonstrated to be inadequate, then supernatural agency must be considered as the next explanation. This mode of explanation, however, is anathema to modern scientists. Unlike the Victorian reliance on induction, the modern adherence to natural causes is not a mere preference: it is a requirement. To fully understand the ramifications of accepting supernatural explanations in science, it is worth considering in detail exactly the circumstances under which ID theorists would have us consider them.
According to the logic of ID, supernatural causation should be considered for a phenomenon when no known natural cause is adequate to explain that phenomenon. In actuality, there are two different paths that a scientist might choose to take when encountering such an inexplicable phenomenon. The first of these paths is to continue exploring. If there is no known natural cause for a phenomenon, then one must dig deeper to reveal a mechanism that is new to science. To follow this path is to assume that scientific inquiry will eventually reveal all of the subtleties of nature.
The second possible path to take when encountering a phenomenon for which no known natural cause exists is to assume that no natural cause exists at all. This is the methodology of ID, which assumes that no known cause means no knowable cause. To follow this path is to assume that there are real gaps in what we can know about nature and that no amount of inquiry will ever fill those gaps. This argument (sometimes called the God of the Gaps argument) is pessimistic not only in its implications for scientific inquiry but also in its theological implications. Though it assumes that there is a limit to what science can understand about the world, it also relegates God to the role of null hypothesis. That is, if God is there only to explain the gaps in our knowledge, then every new discovery diminishes God’s role in the universe.
The God of the Gaps argument actually presents a double-edged sword to its theistic supporters, however. Under this model, closing gaps in our understanding of nature diminishes the role of God. Conversely, every gap in our knowledge (p.155) that is exposed, and for which a miracle is invoked as an explanation, demonstrates a flaw in God’s creation (Van Till 1991). Interestingly, this logic can be traced back to both Paley and Newton. A perfect God should be able to create a universe that is internally coherent. Implying that God must take an active role in such mundane components of the universe as bacterial flagella and amino acid formation does more to denigrate God’s craftsmanship than to verify his existence.
Beyond their inherent epistemological pessimism, there is a more important reason to eschew supernatural causes in science. Accepting the role of a potentially capricious unknowable intelligence in one branch of science undermines not just future discoveries in that one field but all scientific knowledge, past, present, and future. Any physical phenomenon is potentially attributable to the action of supernatural agency. Without specific criteria by which to exclude such agency, any scientific investigation becomes pointless. Every phenomenon would have countless, equally valid explanations. Once biologists accept design by some intelligence as a scientific explanation for the origin of the bacterial flagellum, might geologists not also accept the wrath of that same intelligence as an explanation for the eruption of Mount Pinatubo? If inconstant supernatural agency is a permissible explanation in science, then even the most basic experimentation becomes impossible. How can a chemist be sure that the water in her test tube remained water throughout an entire experiment and did not change, if only briefly, to wine?
These are extreme examples, but they are examples that flow naturally from the logic of ID’s implied methodology, and therefore demonstrate how this logic undermines the scientific method. All theory building is based on some criteria by which scientists favor one explanation over another. Allowing unknowable agency into the panoply of acceptable causal mechanisms undermines those criteria. A mechanism that has no basis for rejection and that is a viable alternative to every other explanation does not simply push the boundaries of science; it re -moves them.
The Intellectual Context of Intelligent Design
In the 1840s, William Whewell and John Stuart Mill helped to pave the way for natural selection by arguing that deductive argument did indeed have a place in the scientific method. In the United States today, there is considerable grassroots effort to have the logical structure of ID accepted as a part of the scientific method. This movement is primarily one aimed at school standards. Advocates for ID want (p.156) it incorporated into high school science curricula and are willing to rewrite state definitions of science to achieve this end. In 2005, ID advocates achieved a notable victory toward this end in Kansas, when the State Board of Education expanded its definition of science to include ID.
An important distinction to draw between Victorian supporters of Darwin’s method and contemporary supporters of the ID method is motivation. Whewell and Mill both wrote in advance of On the Origin of Species and were both presumably unaware of its impending publication. While their expansions of logical practice and scientific method validated Darwin’s argument, they did so a priori. Darwin provided an example of how an independently justified line of inquiry might bear fruit.
The Kansas State Board of Education, however, redefined science for a very different reason. In 2005 Kansas ratified new state science education standards that included a redefinition of science. Under the new standards, science is no longer defined as “the human activity of seeking natural explanations for what we observe in the world around us.” Instead, science is described as “a systematic method of continuing investigation that uses observation, hypothesis testing, measurement, experimentation, logical argument and theory building, to lead to more adequate explanations of natural phenomena” (Proposed Revisions 2004, p. 3). Note that this new definition no longer puts any constraints on what is considered to be an “adequate” scientific explanation.
A 2004 document entitled Proposed Revisions to Kansas Science Standards Draft 1 with Explanations clearly illustrates the motivations of ID advocates. In explaining why the emphasis on natural explanations was dropped from the state science standards, the draft report states, “The current definition of science is intended to reflect a concept called methodological naturalism, which irrefutably assumes that cause and effect laws…are adequate to account for all phenomena and that teleological or design conceptions of nature are invalid…This can be reasonably expected to lead one to believe in the naturalistic philosophy that life and its diversity is the result of an unguided, purposeless natural process” (Proposed Revisions 2004, p. 4). Clearly this is not a case of scientific practices changing and new inquiry resulting from that change. In this case the definition of science is being expanded a posteriori specifically to allow a direction of inquiry that does not meet conventional methodological standards. There is no intellectual justification for this change beyond the desire to consider ID good science.
The most telling change to the Kansas state science standards, and the one that best illustrates the methodological weakness of ID, comes in a surprising place—a (p.157) section of the standards entitled “Teaching with Tolerance and Respect.” In the new standards, the following two sentences have been removed: “If a student should raise a question in a natural science class that the teacher determines to be outside the domain of a science class, the teacher should treat the question with respect. The teacher should explain why the question is outside the domain of natural sciences and encourage the student to discuss the question further with his or her family and other appropriate sources” (Proposed Revisions 2004, p. 6). As an explanation for this change, the document offers the following: “The parameters defining ‘the domain of science’ are ambiguous and scientifically controversial, and thus teachers cannot be expected to be able to accurately identify such questions…. This provision has previously been identified as a mechanism for suppressing classroom discussion that may conflict with Naturalism or scientific materialism, a philosophy that [some people] contend should not guide science education about origins” (Proposed Revisions 2004). Ironically, this change would not have been necessary without the previous change to the definition of science. The ambiguity cited arises entirely from haphazard tinkering with the meaning of science in the earlier section. Under the old standards, the domain of science was easy to define. Science searched for natural causes for natural phenomena. Rewriting the definition of science to include supernatural agency makes the boundaries of science “ambiguous” and “controversial.”
Had Charles Darwin published On the Origin of Species even fifty years earlier, it would have had a significantly more difficult time gaining acceptance. While the strength of his syllogisms and the volume of his evidence may have been the same, his method would have been widely dismissed as pseudoscience by most of the scientific community. It took a separate revolution in the philosophy of science to make the acceptance of Darwin’s noninductive model possible.
By any definition, ID can never be considered science. The type of argument that forms the necessary underpinnings of ID runs counter to scientific inquiry in general. When faced with an unknown, the methodology of ID requires scientists and interested others to resign themselves to the possibility of unknowable phenomena rather than to delve deeper to understand the phenomena.
Perhaps the greatest irony of the modern ID movement is the phraseology of its backers. The largest ID think tank in the United States is the Discovery Institute in Seattle. Fellows at the Discovery Institute argue that we should “teach the (p.158) controversy” in the interest of fostering deeper thinking about scientific issues. In fact, the very logic of ID eschews deep inquiry and discovery in favor of superficial wonder and mystery.
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