Astrology provides the quintessential example of a pseudoscience since it has been tested repeatedly and failed all the tests.
Falsifiability Science and
non-science are often distinguished by the criterion of
falsifiability. The criterion was first proposed by
philosopher of science Karl Popper. To Popper, science does not rely on
induction; instead, scientific investigations are inherently attempts to falsify existing theories through novel tests. If a single test fails, then the theory is falsified. Therefore, any test of a scientific theory must prohibit certain results that falsify the theory, and expect other specific results consistent with the theory. Using this criterion of falsifiability, astrology is a pseudoscience. Astrology was Popper's most frequent example of pseudoscience. Popper regarded astrology as "pseudo-empirical" in that "it appeals to observation and experiment", but "nevertheless does not come up to scientific standards". In contrast to scientific disciplines, astrology does not respond to falsification through experiment. According to Professor of neurology
Terence Hines, this is a hallmark of pseudoscience.
"No puzzles to solve" In contrast to Popper, the philosopher
Thomas Kuhn argued that it was not lack of falsifiability that makes astrology unscientific, but rather that the process and concepts of astrology are non-empirical. To Kuhn, although astrologers had, historically, made predictions that "categorically failed", this in itself does not make it unscientific, nor do the attempts by astrologers to explain away the failure by claiming it was due to the creation of a
horoscope being very difficult (through subsuming, after the fact, a more general horoscope that leads to a different prediction). Rather, in Kuhn's eyes, astrology is not science because it was always more akin to
medieval medicine; they followed a sequence of rules and guidelines for a seemingly necessary field with known shortcomings, but they did no research because the fields are not amenable to research, and so, "They had no puzzles to solve and therefore no science to practise." While an astronomer could correct for failure, an astrologer could not. An astrologer could only explain away failure but could not revise the astrological
hypothesis in a meaningful way. As such, to Kuhn, even if the stars could influence the path of humans through life astrology is not scientific.
Progress, practice and consistency Philosopher
Paul Thagard believed that astrology can not be regarded as falsified in this sense until it has been replaced with a successor. In the case of predicting behaviour, psychology is the alternative. To Thagard a further criterion of demarcation of science from pseudoscience was that the state of the art must progress and that the community of researchers should be attempting to compare the current theory to alternatives, and not be "selective in considering confirmations and disconfirmations". Progress is defined here as explaining new phenomena and solving existing problems, yet astrology has failed to progress having only changed little in nearly 2000 years. To Thagard, astrologers are acting as though engaged in
normal science believing that the foundations of astrology were well established despite the "many unsolved problems", and in the face of better alternative theories (Psychology). For these reasons Thagard viewed astrology as pseudoscience. To Thagard, astrology should not be regarded as a pseudoscience on the failure of Gauquelin to find any correlation between the various astrological signs and someone's career, twins not showing the expected correlations from having the same signs in twin studies, lack of agreement on the significance of the planets discovered since Ptolemy's time and large scale disasters wiping out individuals with vastly different signs at the same time. Rather, his demarcation of science requires three distinct foci: "theory, community [and] historical context". While verification and falsifiability focused on the theory, Kuhn's work focused on the historical context, but the astrological community should also be considered. Whether or not they: • are focused on comparing their approach to others. • have a consistent approach. • try to falsify their theory through experiment. In this approach, true falsification rather than modifying a theory to avoid the falsification only really occurs when an alternative theory is proposed.
Irrationality For the philosopher Edward W. James, astrology is irrational not because of the numerous problems with mechanisms and falsification due to experiments, but because an analysis of the astrological literature shows that it is infused with fallacious logic and poor reasoning. This poor reasoning includes
appeals to ancient astrologers such as Kepler despite any relevance of topic or specific reasoning, and vague claims. The claim that evidence for astrology is that people born at roughly "the same place have a life pattern that is very similar" is vague, but also ignores that time is
reference frame dependent and gives no definition of "same place" despite the planet's moving in the reference frame of the
Solar System. Other comments by astrologers are based on severely erroneous interpretations of basic physics, such as the general belief by medieval astrologers that the
geocentric Solar System corresponded to an atom. Further, James noted that response to criticism also relies on faulty logic, an example of which was a response to twin studies with the statement that coincidences in twins are due to astrology, but any differences are due to "heredity and environment", while for other astrologers the issues are too difficult and they just want to get back to their astrology. Further, to astrologers, if something appears in their favor, they may latch upon it as proof, while making no attempt to explore its implications, preferring to refer to the item in favor as definitive; possibilities that do not make astrology look favorable are ignored.
Quinean dichotomy From the
Quinean web of knowledge, there is a dichotomy where one must either reject astrology or accept astrology but reject all established scientific disciplines that are incompatible with astrology. ==Tests of astrology==