The demarcation problem in the philosophy of science is about how and where to draw the lines around science. The boundries are commonly drawn between science and non-science, science and pseudoscience and of course, between science and religion. A form of this problem, known as the generalized problem of demarcation subsumes all three cases. The generalized problem looks for criteria for deciding which of two theories is the more scientific.
After more than a century of active dialogue, the question of what marks the boundary of science remains fundamentally unsettled. Nonetheless, reasonable consensus exists on certain sub-issues.
Science and religion part ways
The demarcation problem is a fairly recent creation. The problem can be traced back a time when science and religion had already become independent of one another to a great extent. In 1874, the influential science historian John William Draper published his 'History of the Conflict between Religion and Science'. In it he portrayed the entire history of scientific development as a war against religion. This somewhat skewed presentation of historical fact was propagated further by such prestigious followers as Andrew Dickson White in his essay 'A History of the Warfare of Science with Theology in Christendom'.
A number of myths surrounding the history of science owe their popularity to Draper and White. For example, the view that Copernicus held back publication of his De Revolutionibus out of fear of persecution by the church and the idea that medieval Christians believed the earth was flat. Also the personal conflict between Galileo and his one time supporter, Pope Urban VIII was re-written as a battle between Galileo and the church.
Historically speaking, the relationship between science and religion has been more complicated. Many scientists were of course very religious, and religion was often a chief motivator and sponsor of scientific investigation. However towards the end of the 19th century, science and religion came to be seen by the public as being increasingly at odds, a gradual phenomena which came to a head around the debates over the work on evolution produced by Charles Darwin. Precursors and preconditions for the apparent split did exist before Darwin's publication of The Origin of Species, but it was this work which brought the debate into the popular British press and became a figurehead for the tensions between science and religion (a position it essentially still holds today).
The work by Draper and White must be seen as directly coming out of this social climate, and their model of science and religion as being eternally opposed, if not historically accurate, became a dominant social trope.
Logical Positivism
This new conception of science as something not only independent from religion, but actually opposed to it raised the inevitable question of what separates the two. Among the first to develop an answer were the members of the Vienna Circle. Their philosophical position, known as Logical positivism, espoused a theory of meaning which held that only statements about empirical observations are meaningful, effectively asserting that statements which are not derived in this manner (including religious and metaphysical statements) are by nature meaningless (see the verifiability theory of meaning also known as verificationism).
The philosopher Karl Popper noticed that the philosophers of the Vienna Circle had mixed two different problems and had accordingly given them a single solution: verificationism. In opposition to this view, Popper emphasized that a theory might well be meaningful without being scientific, and that, accordingly, a criterion of meaningfulness may not necessarily coincide with a criterion of demarcation. His own falsificationism, thus, is not only an alternative to verificationism; it is also an acknowledgment of the conceptual distinction that previous theories had ignored.
Falsificationism
Popper saw demarcation as a central problem in the philosophy of science. In place of verificationism he proposed falsification as a way of determining if a theory is scientific or not. If a theory is falsifiable, then it is scientific; if it is not falsifiable, then it is not science. Popper uses this criterion of demarcation to draw a sharp line between scientific and unscientific theories. Some have taken this principle to an extreme to cast doubt on the scientific validity of many disciplines (such as macroevolution and Cosmology). Falsifiability was one of the criteria used by Judge William Overton to determine that 'creation science' was not scientific and should not be taught in Arkansas public schools.
Falsifiability is a property of statements and theories, and is itself neutral. As a demarcation criterion, it seeks to take this property and make it a base for affirming the superiority of falsifiable theories over non-falsifiable ones as a part of science, in effect setting up a political position that might be called falsificationism. However, much that would be considered meaningful and useful is not falsifiable. Certainly non-falsifiable statements have a role in scientific theories themselves. The Popperian criterion provides a definition of science that excludes much that is of value; it does not provide a way to distinguish meaningful statements from meaningless ones.
It is nevertheless very useful to know if a statement or theory is falsifiable, if for no other reason than it provides us with an understanding of the ways in which one might assess the theory. One might at the least be saved from attempting to falsify a non-falsifiable theory, or come to see an unfalsifiable theory as unsupportable.
Kuhn and paradigm shifts
Thomas Kuhn, an American historian of science, has proven very influential in the philosophy of science, and is often connected with what has been called postpositivism or postempiricism . In his 1962 book The Structure of Scientific Revolutions, Kuhn divided the process of doing science into two different endeavors, which he called normal science and extraordinary science. The process of "normal" science is what most scientists do while working within the current accepted paradigm of the scientific community, and within this context Karl Popper's ideas on falsification as well as the idea of a scientific method still have some currency. This sort of work is what Kuhn calls "problem solving": working within the bounds of the current theory and its implications for what sorts of experiments should or should not be fruitful. However, during the process of doing "normal" science, Kuhn claimed, anomalies are generated, some of which lead to an extension of the dominant paradigm in order to explain them (like the idea of punctuated equilibrium within the paradigm of evolution), and others for which no satisfactory explanation can be found within the current paradigm. When enough of these anomalies have accumulated, and scientists within the field find them significant (often a very subjective judgment), a "crisis period" is begun, and some scientists begin to participate in the activity of "extraordinary" science. In this phase, it is recognized that the old paradigm is fundamentally flawed and cannot be adapted to further use, and totally new (or often old and abandoned) ideas are looked at, most of which will be failures. But during this time, a new paradigm is created, and after a protracted period of "paradigm shift," the new paradigm is accepted as the norm by the scientific community and integrated into their previous work, and the old paradigm is banished to the history books. The classic example of this is the shift from Maxwellian/Newtonian physics to Einsteinian/Quantum physics in the early 20th century. If the acceptance or failure of scientific theories relied simply on simple falsification, according to Kuhn, then no theory would ever survive long enough to be fruitful, as all theories contain anomalies.
The process by which Kuhn said a new paradigm is accepted by the scientific community at large does indicate one possible demarcation between science and pseudoscience, while rejecting Popper's simple model of falsification. Kuhn instead argued that a new paradigm is accepted mainly because it has a superior ability to solve problems that arise in the process of doing normal science. That is, the value of a scientific paradigm is its predictive power and its ability to suggest solutions to new problems while continuing to satisfy all of the problems solved by the paradigm that it replaces. Pseudoscience can then be defined by a failure to provide explanations within such a paradigm.
Feyerabend and the problem of autonomy in science
There has been a post-Kuhn trend to downplay the difference between science and non-science, as Kuhn's work largely called question to the Popperian ideal of simple demarcation, and emphasized the human, subjective quality of scientific change. The radical philosopher of science Paul Feyerabend took these arguments to their limit, arguing that science does not occupy a special place in terms of either its logic or method, so that any claim to special authority made by scientists cannot be upheld. This leads to a particularly democratic and anarchist approach to knowledge formation. He claimed that there can be found no method within the history of scientific practice which has not been violated at some point in the advancing of scientific knowledge. Both Lakatos and Feyerabend suggest that science is not an autonomous form of reasoning, but is inseparable from the larger body of human thought and inquiry. If so, then the questions of truth and falsity, and correct or incorrect understanding are not uniquely empirical. Many meaningful questions can not be settled empirically -- not only in practice, but in principle.
According to this way of thinking, the difficulty string theorists have had in applying experimental science would not bring in to question their status as scientists.
Conclusion
If observation cannot act as a theory-independent foundation for the scientific enterprise, science becomes a cycle of hypothesising and verification embedded in a theoretical framework and tied to the 'real world' by the agreement of the scientific community. Popper's claim that only falsifiable statements are scientific does not help here. The Quine-Duhem thesis argues that it is not possible to prove that a statement is falsified; rather, falsification occurs when the scientific community agrees that a statement is falsified.
Assuming this to be true, it is not obvious how scientific debate differs in any logical way from the debates of, for example, historians. Both work within a cycle of hypothesising and verification, historians by reference to historical documents (the past), scientists by reference to the experiments they propose to construct (the future).
One might argue that science occupies a special place because its experiments can be repeated, but using repetition as a demarcation criterion would disenfranchise areas that are at present considered to be science, such as palaeontology and cosmology.
Owing to its esoteric nature, the demarcation problem is not widely recognized even among scientists. Outside of academic circles, Popper's philosophy has gained a smattering of populararity, his falsificationism often being heralded as the last word on demarcation. Despite this popular vote in favor of falsificationism, for professional philosophers of science, the demarcation problem is generally considered unresolved. It is not, however a purely academic problem. In its 1993 Daubert v. Merrell Dow opinion, the United States Supreme Court articulated a set of criteria for the admissibility of scientific expert testimony, in effect developing their own demarcation criteria. The four Daubert criteria are,
- The theoretical underpinnings of the methods must yield testable predictions by means of which the theory could be falsified.
- The methods should preferably be published in a peer-reviewed journal.
- There should be a known rate of error that can be used in evaluating the results.
- The methods should be generally accepted within the relevant scientific community.
In 1999 the Court extended Daubert's general holding to include non-scientific expert testimony as well. The question of where the boundries of science lie is no longer one that affects only the funding and status of scientific enterprises. It now impinges on the social and juridical treatment of us all.
