Where is the boundary between science and non-science? How can the scientific legitimacy of parapsychology be assessed?

In this blog post, we will review the scientific and philosophical distinctions and debates surrounding the scientific legitimacy of parapsychology.

 

Parapsychology is the study of paranormal psychological phenomena related to psychic powers, the spiritual world, spiritual beings, and spiritual abilities. Parapsychology was not recognized as a science for many years, gaining official recognition in 1969 when the American Association for the Advancement of Science recognized the Parapsychological Society as a cooperating organization. However, many scientists were unhappy with this decision, considering parapsychology a pseudoscience. So, is parapsychology a science? What is science in the first place?
The problem of distinguishing science from non-science is known as the compartmentalization problem in philosophy of science. It is a central problem in the philosophy of science and was first challenged by E. Mach, J. H. Poincare, P. Duhem, and others, and was the goal of logical positivists such as L. Wittgenstein, M. Schlick, R. Carnap, and H. Reichenbach. It was also a major concern of K. Popper’s methodological reflections on science. Philosophers of science have each argued for criteria for distinguishing science from non-science. The early logical positivists proposed the criterion of verifiability, while later logical positivists and logical empiricists described it as the criterion of confirmability. Popper pointed out the problems with these criteria and proposed the criterion of disprovability.
However, Popper’s criteria were also criticized by the ‘new philosophy of science’ proposed by T. S. Kuhn, N. R. Hanson, P. K. Feyerabend, and others. In this essay, I will criticize the criteria of logical positivism, logical empiricism, and disproversialism, respectively, from the perspective of the new philosophy of science. Furthermore, I will criticize the various criteria for categorization proposed in the philosophy of science and reveal the problems that need to be overcome to solve the problem of categorization.
First, we can say that logical positivism is a combination of Comte and Mill’s positivism and modern logic in the 20th century. Logical positivists accept Mach’s position that modern science is based on direct experience and that scientific theories are derived from inductive generalizations about observational data. They hold the phenomenalist position that scientific inquiry begins with unquestionable observations, which must be translated into a neutral observational language that is completely independent of all theories. Therefore, the philosophy of science of logical positivists aims to establish the basic concepts of science and analyze scientific sentences. They recognized a scientific theory as a “deductive formal system of scientific propositions” and viewed it as a “system of meaningful propositions,” so only scientific propositions are epistemically meaningful. For them, the distinction between science and non-science and the distinction between meaning and meaninglessness are the same, and the criteria of science and non-science coincide with the criteria of meaningfulness.
They also argued for the principle of verification as a criterion of meaningfulness, which led them to introduce the criterion of verifiability. This criterion states that for a proposition to be meaningful, it must be verifiable. By this criterion, they tried to distinguish scientific propositions from meaningless ones. However, the only meaningful propositions that can be conclusively verified by this criterion are those that are reducible to historical or observational propositions that can be directly verified by current perception. The problem with this criterion is that it makes all normative philosophy, value philosophy, ethics, and aesthetics, including metaphysical propositions, as well as general propositions, propositions about the past and future, and even scientific laws expressed as universal propositions, meaningless and unscientific. As a result, logical positivists abandoned the criterion of conclusive verifiability because they could not solve this problem.
Next, logical empiricists, who emerged after logical positivism, proposed a weaker criterion of verifiability, called confirmability. More specifically, a concept is verifiable if the propositions to which it is applied can be verified, even if only slightly, then the concept is meaningful and is called verifiable. The problem of logical empiricism, as they argue, is to analyze the corroboration relationship between scientific laws and the observational statements that confirm or disprove them, and to analyze how scientific concepts become meaningful.
According to the criterion of confirmability, a proposition is meaningful if it can be empirically confirmed. For example, the law of universal gravitation, the law of thermodynamics, the law of constant proportions, the law of heredity, etc. are universal propositions that say that under certain conditions, they occur everywhere and at any time, and this is empirically confirmed. The core of the theory of confirmation is that such empirically confirmed propositions are also considered meaningful propositions. So, can propositions that have been rejected as meaningless be meaningful, which is the problem faced by logical positivists? The answer to this question is yes. Many general propositions, including scientific laws, can be confirmed by direct propositions that can be derived from them.
In addition, propositions about the past, the future, and the minds of others can be verified by inductive reasoning from direct observation and by the behavior of others, respectively. Metaphysical propositions remain nonsensical because there is no evidence for their verification or direct propositions derived from them. This criterion of verifiability may seem to be a successful distinction that solves the problems faced by the previous verifiability criterion. However, this theory of confirmation runs into a logical problem called the “reverse logic of confirmation”. As an example, consider the problematic hypothesis “all crows are black”: any object that is neither a crow nor black can be presented as confirming this hypothesis, except for black crows. To put it more simply, the hypothesis ‘all crows are black’ and the hypothesis ‘all non-black things are not crows’ are logically equivalent, so a white swan that is neither a crow nor black would confirm the hypothesis ‘all crows are black’. The conclusion we draw from this discussion is that the criterion of confirmability can be questioned on the grounds that the inductive method cannot be logically justified.
Finally, Popper pointed out the inadequacy of the criteria of meaningfulness of logical positivism and logical empiricism as a distinction between science and non-science, and tried to propose a new distinction. He criticized the significance criteria of verifiability and corroborability on three grounds. First, they are fundamentally inadequate; second, because they are based on an inductive view of science, their criteria violate their own logical justification by inductive logic. Third, they criticize that the criterion of significance renders meaningless even the natural sciences, which are not reducible to fundamental statements. This makes their criterion ineffective as a distinction between science and non-science.
Popper abandons inductivism and the notion of a purely empirical basis for science and proposes the criterion of disprovability as a purely scientific and non-scientific distinction, rather than the criterion of significance. According to him, in order for a proposition to be recognized as having scientific status, it must be disprovable. Popper says that universal propositions cannot be derived from propositional propositions, but that they are contradictory because they are contradicted by propositional propositions, and consequently it is possible to demonstrate the falsity of universal propositions from the truth of propositional propositions by pure deductive reasoning.
According to this criterion, the distinction between science and pseudoscience is not meaningless, but metaphysical and pseudoscientific, and the criterion of disprovability that separates them is based on his five rules of scientific method (problem – new theory – deduction of propositions – attempted refutation – competition between theories). Popper’s criteria of disprovability can be seen as solving the problems faced by logical positivists and logical empiricists mentioned above. However, the assumptions of his methodological rules can still be criticized: Popper also presupposes a purely observational basis for science and is not exempt from the bias to understand scientificity only in terms of the logical aspects of science. This is criticized by Kuhn, Firevent, and others.
We have criticized both the logical positivist, logical empiricist, and antipositivist views of the divide and found that they all have three common problems with being perfect divisions. The first is the idea of pure observation and neutrality independent of the most basic theories of science, the second is the idea of science as satisfying inductive or deductive rules, and the third is the idea that it is possible to distinguish between discoveries in science and their justification. These problems lead to another debate about the distinction between science and non-science without resolving it. However, the division criteria proposed by these divisionists do not remain merely a subject of debate; their common problem is that they are not only methodological and prescriptive, but also give rise to attempts to solve the division problem through a postmethodological and historical perspective.