Demarcation problem
In philosophy of science and epistemology, the demarcation problem is the question of how to distinguish between science and non-science. It also examines the boundaries between science, pseudoscience and other products of human activity, like art and literature and beliefs. The debate continues after more than two millennia of dialogue among philosophers of science and scientists in various fields. The debate has consequences for what can be termed "scientific" in topics such as education and public policy.
The ancients
An early attempt at demarcation can be seen in the efforts of Greek natural philosophers and medical practitioners to distinguish their methods and their accounts of nature from the mythological or mystical accounts of their predecessors and contemporaries.G. E. R. Lloyd noted that there was a sense in which the groups engaged in various forms of inquiry into nature attempt to "legitimate their own positions", laying "claim to a new kind of wisdom ... that purported to yield superior enlightenment, even superior practical effectiveness". Medical writers of the Hippocratic tradition maintained that their discussions were based on demonstration of logical necessity, a theme developed by Aristotle in his Posterior Analytics. One element of this polemic for science was an insistence on a clear and unequivocal presentation of arguments, rejecting the imagery, analogy, and myth of the old wisdom. Some of their claimed naturalistic explanations of phenomena have been found to be quite fanciful, with little reliance on actual observations.
Cicero's De Divinatione implicitly used five criteria of scientific demarcation that are also used by modern philosophers of science.
Logical positivism
, formulated during the 1920s, is the idea that only statements about matters of fact or logical relations between concepts are meaningful. All other statements lack sense and are labelled "metaphysics".According to A. J. Ayer, metaphysicians make statements which claim to have "knowledge of a reality which the phenomenal world". Ayer, a member of the Vienna Circle and a noted English logical-positivist, argued that making any statements about the world beyond one's immediate sense-perception is impossible. This is because even metaphysicians' first premises will necessarily begin with observations made through sense-perception.
Ayer implied that the demarcation occurs when statements become "factually significant". To be "factually significant", a statement must be verifiable. In order to be verifiable, the statement must be verifiable in the observable world, or facts that can be induced from "derived experience". This is referred to as the "verifiability" criterion.
This distinction between science, which in the opinion of the Vienna Circle possessed empirically verifiable statements, and what they pejoratively termed "metaphysics", which lacked such statements, can be considered as representing another aspect of the demarcation problem. Logical positivism is often discussed in the context of the demarcation between science and non-science or pseudoscience. However, "The verificationist proposals had the aim of solving a distinctly different demarcation problem, namely that between science and metaphysics."
Falsifiability
considered demarcation as a major problem of the philosophy of science. Popper articulates the problem of demarcation as:Falsifiability is the demarcation criterion proposed by Popper as opposed to verificationism: "statements or systems of statements, in order to be ranked as scientific, must be capable of conflicting with possible, or conceivable observations."
Against verifiability
Popper rejected solutions to the problem of demarcation that are grounded in inductive reasoning, and so rejected logical-positivist responses to the problem of demarcation. He argued that logical-positivists want to create a demarcation between the metaphysical and the empirical because they believe that empirical claims are meaningful and metaphysical ones are not. Unlike the Vienna Circle, Popper stated that his proposal was not a criterion of "meaningfulness".Popper argued that the Humean induction problem shows that there is no way to make meaningful universal statements on the basis of any number of empirical observations. Therefore, empirical statements are no more "verifiable" than metaphysical statements.
This creates a problem for the demarcation the positivists wanted to define between the empirical and the metaphysical. By their very own "verifiability criterion", Popper argued, the empirical is subsumed into the metaphysical, and the demarcation between the two becomes non-existent.
The solution of falsifiability
In Popper's later work, he stated that falsifiability is both a necessary and sufficient criterion for demarcation. He described falsifiability as a property of "the logical structure of sentences and classes of sentences", so that a statement's scientific or non-scientific status does not change over time. This has been summarized as a statement being falsifiable "if and only if it logically contradicts some sentence that describes a logically possible event that it would be logically possible to observe".Kuhnian postpositivism
, an American historian and philosopher of science, is often associated with what has been termed 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 termed normal science and extraordinary science, the latter of which introduces a new "paradigm" that solves new problems while continuing to provide solutions to the problems solved by the preceding paradigm.Popper criticized Kuhn's demarcation criterion, saying that astrologers are engaged in puzzle solving, and that therefore Kuhn's criterion recognized astrology as a science. He stated that Kuhn's criterion results in a "major disaster ... replacement of a rational criterion of science by a sociological one".
Feyerabend and Lakatos
Kuhn's work largely called into question Popper's demarcation, and emphasized the human, subjective quality of scientific change. Paul Feyerabend was concerned that the very question of demarcation was insidious: science itself had no need of a demarcation criterion, but instead some philosophers were seeking to justify a special position of authority from which science could dominate public discourse. Feyerabend argued that science is not in fact special in terms of either its logic or method, and no claim to special authority made by scientists can be sustained. He argued that, within the history of scientific practice, no rule or method can be found that has not been violated or circumvented at some point in order to advance scientific knowledge. Both Imre 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.Thagard
proposed another set of principles to try to overcome these difficulties, and argued that it is important for society to find a way of doing so. According to Thagard's method, a theory is not scientific if it satisfies two conditions:- The theory has been less progressive than alternative theories over a long period of time, and has many unsolved problems; and...
- The community of practitioners makes little attempt to develop the theory towards solutions of the problems, shows no concern for attempts to evaluate the theory in relation to others, and is selective in considering confirmations and disconfirmations.
Thagard also stated that his criteria should not be interpreted so narrowly as to allow willful ignorance of alternative explanations, or so broadly as to discount our modern science compared to science of the future. His definition is a practical one, which generally seeks to distinguish pseudoscience as areas of inquiry which are stagnant and without active scientific investigation.