Science and Pseudoscience

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Since the rise of modern science in the sixteenth and seventeenth centuries, attempts to adjudicate the difference between science and pseudoscience have always been more than an exercise in academic debate. The religious, political, and social implications of how science is defined, who defines it, and who and what is left out of the definition has been a contentious one. Today, the term pseudoscience is often employed by those in the scientific community to disparage claims to scientific credibility that, in fact, lack evidence or fail to employ the methods of science. Pseudoscience is only one term used to contrast with science; others include, on the neutral side, nonscience, protoscience, prescience, frontiers science, and borderlands science ; and on the pejorative side, pathological science, junk science, voodoo science, crackpot science, and bad science.

With the ascendancy of science in the seventeenth century other knowledge traditions began to employ the empirical methods of science to gain respectability. The study of demons, witches, and spirits, for example, took a decidedly empirical turn in the early modern period, out of religious concerns that atheism might ascend to social respectability along with science. One observer wrote, "Atheists abound in these days and witchcraft is called into question. If neither possession nor witchcraft (contrary to what has been so long generally and confidently affirmed), why should we think that there are devils? If no devils, no God" (Walker, pp. 7172). By the nineteenth century the study of such quasi-scientific ideas as phrenology, mesmerism, and spiritualism was organized through scientific societies, such as the Society for Psychical Research, founded in London in 1882, and the American Society for Psychical Research, founded in Boston in 1885, both of which included as active members prominent scientists.

The Demarcation Problem

In the twentieth century the philosophy of science developed into a viable academic discipline, out of which grew attempts to delimit science and nonscience traditions. In The Logic of Scientific Discovery, for example, the philosopher of science Karl Raimund Popper identified what he called "the problem of demarcation," that is "the problem of finding a criterion which would enable us to distinguish between the empirical sciences on the one hand, and mathematics and logic as well as 'metaphysical' systems on the other" (1934, p. 27). Most scientists and philosophers use induction as the criterion of demarcationif one reasons from particular observations or singular statements to universal theories or general conclusions, then one is doing empirical science. Popper's thesis was that induction does not actually provide empirical proof"no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white" (p. 34)and that, de facto, scientists actually reason deductively, from the universal and general to the singular and particular. But in rejecting induction as the preferred (by others) criterion of demarcation between science and nonscience, Popper was concerned that his emphasis on deduction would lead to an inevitable fuzziness of the boundary line. If a scientific theory can never actually be proven, then is science no different from other knowledge disciplines?

Popper's solution to the problem of demarcation was the criterion of falsifiability. Theories are "never empirically verifiable," but if they are falsifiable then they belong in the domain of empirical science. "In other words: I shall not require of a scientific system that it shall be capable of being singled out, once and for all, in a positive sense; but I shall require that its logical form shall be such that it can be singled out, by means of empirical tests, in a negative sense: it must be possible for an empirical scientific system to be refuted by experience" (1934, p. 70). The theory of evolution, for example, has been accused by creationists as being nonscientific because no one was there to see it happen and biologists cannot observe it in the laboratory because it takes too long. But, in fact, by Popper's criterion of falsifiability, the theory of evolution would be doomed to the trash heap of bad science if, say, human fossil remains turned up in the same geological bedding planes as 300-million-year-old trilobites. No such falsification of evolution has ever been found, and although by Popper's criterion this does not mean that the theory has been proven absolutely, it does mean that it has yet to be falsified, thus placing it firmly in the camp of solid empirical science.

Science Defended, Science Defined

The evolution-creationism controversy, in fact, has provided both scientific and legal forms of demarcation between science and pseudoscience. It is one thing for academic scientists and philosophers to debate the definition of science; it is another matter when the U.S. Supreme Court weighs in on the issue. Because evolution could not be excluded from public school science classrooms in the early twentieth century, and because the teaching of religious tenets was deemed unconstitutional in a number of state trials in the middle of the twentieth century, in the latter part of the century creationists began to call their doctrines creation-science. Since academic openness calls for a balanced treatment of competing ideas, they argued, creation-science should be taught side by side with evolution-science. In 1982 creationists succeeded in getting passed the Louisiana Balanced Treatment for Creation-Science and Evolution Science Act. In 1985 the law was struck down in the Federal Court of Louisiana, a decision that was appealed to the U.S. Court of Appeals for the Fifth Circuit. In 1986 the U.S. Supreme Court agreed to hear the case, leading to the publication of a remarkable document that clearly and succinctly adjudicated (literally in this case) the difference between science and pseudoscience.

The document was an amicus curiae brief submitted to the court on behalf of seventy-two Nobel laureates in science, seventeen state academies of science, and seven other scientific organizations. The amicus brief begins by offering a general definition: "Science is devoted to formulating and testing naturalistic explanations for natural phenomena. It is a process for systematically collecting and recording data about the physical world, then categorizing and studying the collected data in an effort to infer the principles of nature that best explain the observed phenomena." Next, the scientific method is discussed, beginning with the collection of "facts," the data of the world. "The grist for the mill of scientific inquiry is an ever increasing body of observations that give information about underlying 'facts.' Facts are the properties of natural phenomena. The scientific method involves the rigorous, methodical testing of principles that might present a naturalistic explanation for those facts" (1986, p. 23).

Based on well-established facts, testable hypotheses are formed. The process of testing "leads scientists to accord a special dignity to those hypotheses that accumulate substantial observational or experimental support." This "special dignity" is called a "theory" that, when it "explains a large and diverse body of facts" is considered "robust" and if it "consistently predicts new phenomena that are subsequently observed" it is "reliable." Facts and theories are not to be used interchangeably or in relation to one another as more or less true. Facts are the world's data. Theories are explanatory ideas about those facts. "An explanatory principle is not to be confused with the data it seeks to explain." Constructs and other nontestable statements are not a part of science. "An explanatory principle that by its nature cannot be tested is outside the realm of science" (pp. 2324).

It follows from the nature of scientific method that no explanatory principles in science are final. "Even the most robust and reliable theory is tentative. A scientific theory is forever subject to reexamination andas in the case of Ptolemaic astronomymay ultimately be rejected after centuries of viability." Scientists encounter uncertainty as a regular and natural part of their work. "In an ideal world, every science course would include repeated reminders that each theory presented to explain our observations of the universe carries this qualification: 'as far as we know now, from examining the evidence available to us today'" (1986, p. 24). Science also seeks only naturalistic explanations for phenomena. "Science is not equipped to evaluate supernatural explanations for our observations; without passing judgment on the truth or falsity of supernatural explanations, science leaves their consideration to the domain of religious faith" (p. 23). According to the amicus any body of knowledge accumulated within the guidelines previously described is considered scientific and suitable for public school science education; and any body of knowledge not accumulated within these guidelines is not considered scientific.

On June 19, 1987, the U.S. Supreme Court, by a vote of 7 to 2, held that the Louisiana Act "is facially invalid as violative of the Establishment Clause of the First Amendment, because it lacks a clear secular purpose" and that "[t]he Act impermissibly endorses religion by advancing the religious belief that a supernatural being created humankind" (Edwards v. Aguillard, 1987). The Louisiana trial in general, and the amicus brief in particular, had the effect of temporarily galvanizing the scientific community into defining science as a body of knowledge accumulated through a particular scientific method, as defined by the leading members of the scientific community themselves. Science is as scientists do.

Delimiting the Boundaries between Science and Pseudoscience

Creation-science (and its most recent hybrid, intelligent design theory) is just one of many claims that most mainstream scientists reject as pseudoscience. But what about those claims to scientific knowledge that are not so obviously classified as pseudoscience? When encountering a claim, how can one determine whether it constitutes a legitimate assertion as scientific? What follows is a list of ten questions that get to the heart of delimiting the boundaries between science and pseudoscience:

  1. How reliable is the source of the claim? All scientists make mistakes, but are the mistakes random, as one might expect from a normally reliable source, or are they directed toward supporting the claimants' preferred beliefs? Scientists' mistakes tend to be random; pseudoscientists' mistakes tend to be directional.
  2. Does this source often make similar claims? Pseudoscientists have a habit of going well beyond the facts, and so when individuals make many extraordinary claims, they may be more than iconoclasts. What one is looking for here is a pattern of fringe thinking that consistently ignores or distorts data.
  3. Have the claims been verified by another source? Typically, pseudoscientists make statements that are unverified or are verified by a source within their own belief circle. One must ask who is checking the claims and even who is checking the checkers.
  4. How does the claim fit with what is known about how the world works? An extraordinary claim must be placed in a larger context to see how it fits. When people claim that the pyramids and the Sphinx were built more than 10,000 years ago by an advanced race of humans, they are not presenting any context for that earlier civilization. Where are its works of art, weapons, clothing, tools, and trash?
  5. Has anyone made an effort to disprove the claim or has only confirmatory evidence been sought? This is the confirmation bias or the tendency to seek confirmatory evidence and reject or ignore disconfirmatory evidence. The confirmation bias is powerful and pervasive. This is why the scientific method, which emphasizes checking and rechecking, verification and replication, and especially attempts to falsify a claim, is critical.
  6. Does the preponderance of evidence converge on the claimant's conclusion or a different one? The theory of evolution, for example, is proved through a convergence of evidence from a number of independent lines of inquiry. No single fossil or piece of biological or paleontological evidence has the word evolution written on it; instead, there is a convergence from tens of thousands of evidentiary bits that adds up to a story of the evolution of life. Creationists conveniently ignore this convergence, focusing instead on trivial anomalies or currently unexplained phenomena in the history of life.
  7. Is the claimant employing the accepted rules of reason and tools of research or have those rules and tools been abandoned in favor of others that lead to the desired conclusion? UFOlogists exhibit this fallacy in their continued focus on a handful of unexplained atmospheric anomalies and visual misperceptions by eyewitnesses while ignoring that the vast majority of UFO sightings are fully explicable.
  8. Has the claimant provided a different explanation for the observed phenomena or is it strictly a matter of denying the existing explanation? This is a classic debate strategy: Criticize your opponent and never affirm what you believe to avoid criticism. This strategy is unacceptable in science.
  9. If the claimant has proffered a new explanation, does it account for as many phenomena as does the old explanation? For a new theory to displace an old theory, it must explain what the old theory did and then some.
  10. Do the claimants' personal beliefs and biases drive the conclusions or vice versa? All scientists have social, political, and ideological beliefs that potentially could slant their interpretations of the data, but at some point, usually during the peer-review system, those biases and beliefs are rooted out or the paper or book is rejected for publication.

The Enchanted Glass of Science

At the dawn of the scientific revolution in the early seventeenth century, the English philosopher Francis Bacon sought to turn away from the scholastic tradition of logic and reason as the sole road to truth, as well as reject the Renaissance quest to restore the perfection of ancient Greek knowledge. In his 1620 work Novum Organum (New Tool, contrary to the opinion of Aristotle's Organon ), Bacon portrayed science as humanity's savior that would inaugurate a restoration of all natural knowledge through a proper blend of observation and logic, data and theory. Bacon understood, however, that there are significant social and psychological barriers that interfere with one's understanding of the natural world, "For the mind of man is far from the nature of a clear and equal glass, wherein the beams of things should reflect according to their true incidence; nay, it is rather like an enchanted glass, full of superstition and imposture, if it be not delivered and reduced" (p. 53). In the end, thought Bacon, science offers the best hope to deliver the mind from such superstition and imposture. Today, science continues to deliver on that hope.

See also Evolutionary Theory (Natural Selection); Philosophy of Science, Problems of; Popper, Karl Raimund.


Amicus Curiae Brief of 72 Nobel Laureates, 17 State Academics of Science, and 7 Other Scientific Organizations, in Support of Appellees, Submitted to the Supreme Court of the United States, October Term, 1986, as Edwin W. Edwards, in His Official Capacity as Governor of Louisiana, et al., Appellants v. Don Aguillard et al., Appellees, 1986.

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Michael Shermer (2005)

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Science and Pseudoscience

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Science and Pseudoscience