---
title: "Demarcation problem"
chunk: 1/3
source: "https://en.wikipedia.org/wiki/Demarcation_problem"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:36:27.454881+00:00"
instance: "kb-cron"
---

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.

Aristotle described at length what was involved in having scientific knowledge of something. To be scientific, he said, one must deal with causes, one must use logical demonstration, and one must identify the universals which 'inhere' in the particulars of sense. But above all, to have science one must have apodictic certainty. It is the last feature which, for Aristotle, most clearly distinguished the scientific way of knowing.
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 ==

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" (see the verifiability theory of meaning also known as verificationism).
According to A. J. Ayer, metaphysicians make statements which claim to have "knowledge of a reality which [transcends] 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 ==

Karl Popper considered demarcation as a major problem of the philosophy of science. Popper articulates the problem of demarcation as:

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, I call the problem of demarcation."
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's demarcation criterion has been criticized both for excluding legitimate science ... and for giving some pseudosciences the status of being scientific ... According to Larry Laudan (1983, 121), it "has the untoward consequence of countenancing as 'scientific' every crank claim which makes ascertainably false assertions". Astrology, rightly taken by Popper as an unusually clear example of a pseudoscience, has in fact been tested and thoroughly refuted ... Similarly, the major threats to the scientific status of psychoanalysis, another of his major targets, do not come from claims that it is untestable but from claims that it has been tested and failed the tests.
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 (empirical) sentence that describes a logically possible event that it would be logically possible to observe".