Criticism of astrology in the light of allegations regarding its pseudo-scientific nature

Robert Marzewski

” The fact that astrology is a pseudoscience does not raise any doubts, at least among philosophers. However, the explanation of why this is so, is by no means obvious. ” 1 
Jacek Cachro
       In some respects, the subject of this study may seem banal to some people. It is so because arguments against astrology often show that their authors know little about astrology, but also because criteria of science are understood by them in a way that leaves much to be desired. At the same time, however, the task I set myself is difficult. It is not easy to talk about obvious things. It is often the case that the pseudo-scientific character of astrology is assumed in advance, and the reliability of tools supporting such assumption remains a secondary issue. One can ask is all kinds of inquiries are reasonable since their result is already known in a way.
But it can also be that something that seems obvious to one person, does not need to be so to others, not because they are wrong, but because this “obviousness” is a matter of debate or even strongly doubtful. However, it is worth presenting your position even if it is just to confront it with different views.
It must also be admitted that there are reliable researchers who approach the subject with great care. Then, it turns out that astrology, even if approached with the sincerest intentions, would be difficult to be considered science and the present text by no means claims to change such state of affairs.

Confirmation error

The confirmation error is a serious charge against astrology. It involves selective treatment of information, i.e. focusing only on those that confirm one’s thesis while ignoring facts that contradict it.
It should be noted that – just like the Forer effect – also the confirmation error has quite broad references to many areas of human cognitive activity and is not a phenomenon distinguishing itself particularly in the context of astrology due to its own nature. All the more, it cannot be assumed that the belief in the credibility of astrology is based on the confirmation error. If we said so, then it would be necessary to refer to all astrologers in modern times, but also in the past and the future. However, if there was at least one astrologer who would see that his or another astrologer’s claims were wrong, it would mean that the confirmation error occurs in a gradual manner. Of course, it is not difficult to find a situation where astrologers are wrong and confirm the facts themselves. In other words, they admit that claims basing on the astrological knowledge may be wrong, or more generally, they may be more distant or closer to the truth.
It can be said that claiming that the use of astrology is based on the confirmation error would as such be subject to such error because it would ignore facts in the case of which such phenomenon does not occur.

Confirmation in the philosophy of science

       At the same time, it is difficult not to notice that in fact, astrologers may have a tendency to such a selective treatment of reality. In this respect, however, they do not constitute a distinguished group, free from such ailments. This tendency is normal not only to so-called ordinary people but also to scientists, and there was also a time when, according to the generally adopted interpretation of the philosophy of science, the confirmation rule used to decide what should be considered science and what should not. Of course, at that time the phenomenon functioned in a different context, i.e. not as a type of false or selective perception of reality.

Moritz Schlick the founding father of Vienna Circle
Moritz Schlick the founding father of Vienna Circle

Philosophers and scientists gathered around the Vienna Circle, representing the trend known as neo-positivism or logical empiricism, at the beginning of the last century wondered how to set the boundaries of science, which in turn would enable understanding of its fundamental problems. Science was perceived by them as a method of achieving solid, indisputable knowledge, in contrast to metaphysics, which, after closer analysis, did not contribute anything to knowledge, because it could only be formulated with sentences without any sense, i.e. those that were not empirically confirmed. Initially, the criterion separating the two areas was verification, i.e. the possibility of stating the truth or falseness of the statements. However, soon the creators of such an interpretation realized that by following it, they essentially undermine the truthfulness of the laws of science because they are general statements that cannot be expressed in a finite number of empirical observations. That is why the confirmation rule was introduced as a binding criterion, which, although it did not guarantee the veracity of general sentences, could make them more probable. It basically meant that the bigger number of empirical facts or facts that could be considered empirical confirmed a given theory, the more probable the theory was. It can be easily noticed that such an approach is nothing but a confirmation error.
Being aware that my reasoning may turn out to be wrong, I cannot refrain from recording observations that are obvious to me:

  • the reasoning of the followers of the Vienna Circle was burdened with a confirmation error
  • if astrology is claimed to be based on the aforementioned error, then in this respect it does not differ from scientific claims as understood by the followers of the Vienna Circle
  • it should be assumed that if one observes facts confirming the validity of the rules of astrology, then according to the interpretation of the Vienna Circle, it should be considered as a scientific field.

Of course, this is not so easy, because we should ask a question about the nature of empirical facts, based on which the confirmation would be based. These can be divided into two types:

  • physical facts related to the hypothetical mechanism of astrology
  • facts based on the assumptions resulting from interpretation of horoscopes

Lack of physical confirmation

       When it comes to the first type of facts, the topic is discussed by the critics of astrology very willingly, and this is because no facts of a physical nature that would indicate how astrology works have been discovered so far and nothing indicates that this state of affairs is about to change in the near future. There is a whole lot of examples relating to this argument. I am probably not able to list all of them, but to have some picture of what I am talking about, I will quote some of them:

  1. Zodiac does not overlap with the relevant constellations. The problem of the thirteenth sign of the Zodiac.
  2. Science has not discovered any cosmic and explanatory effects of fluidic astrology.
  3. Earth obscures some planets and stars, preventing humans from being influenced by the hypothetical cosmic fluids.
  4. Stars are too distant to affect life on Earth.
  5. A considerable distance of the stars disturbs calculations of astrologers. For example, from Jupiter, light (running at the highest known speed) reaches the Earth after about 43 minutes. For stars, these would be much larger time intervals. All the more so it should apply to hypothetical fluids.
  6. The gravity of the Earth and objects situated on the Earth is disproportionately large compared to the gravity of other planets.
  7. Ancient astrologers did not take into account trans-cosmic planets, and horoscopes were still supposed to be true.
  8. Astrology is subject to magical thinking and is based on mythology.

Referring to the above objections, it should be first of all said that they are groundless as astrologers do not postulate the existence of any mysterious cosmic fluids that would explain some alleged cause and effect mechanism. Perhaps such a mechanism exists, but even if it so, it is not necessary to know it to accept the effectiveness of astrology. The philosopher of science Paul Thagard 2 and the already mentioned Jacek Cachro 3 argue that the harmfulness of smoking was recognized on the basis of statistical regularities.

It can also be said that the law of gravity is not questioned, although we know only computational rules and empirical predictions that confirm it but still, no hypothetical graviton or gravitational waves have been discovered. In other words, it cannot be claimed that the mechanism of gravity has been discovered.

In order to keep the aforementioned examples of allegations against astrology in force, many other negative consequences for science would have to be accepted. And so in reference to point 1, it should be noted that astronomers also use the tropical zodiac, but somehow nobody criticises them for doing it, nor postulates shifting astronomical seasons or Easter.

As for point 2, although astrologers do not insist on the existence of such fluids, this argument suggests that all possible influences have already been discovered, which, in turn, shuts off all the possibilities of development for science. This argument is all the more unjustified, that scientists now claim that only 5% of the Universe is available to our observations, while about 27% is dark matter, and about 68% is dark energy.

As far as point 3 is concerned, it is challenged at least by the existence of a neutrino, for which penetration through a planet such as Earth is not a major problem.

It’s hard to say what points 4 and 5 actually they refer to, apart from the distance. They assume not only the existence of some fluids, but also suggest their properties.

And as for point 6, it should get justified why it is assumed that astrology is based on gravitational interactions.

Point 7, in turn, also undermines the achievements of science. Newton’s theory for more than two centuries was considered right. And even after Einstein, it finds application in some areas, such as ballistics or construction, because calculations based on the theory are simpler and effective enough. The same applies to, for example, modern horary astrology, in which the trans-Saturnian planets are omitted.

In point 8, we deal with another shot in a dignified scientific foot. For example, chemistry is derived from alchemy, and no one discredits it. In addition, it should be noted that the origin of a given theory is completely irrelevant. Ideas of scientific hypotheses can come from anywhere, for example, they may be dreamt of, just as the atomic model of Niels Bohr was inspired by his dream, and similarly, August Friedrich Kekule saw a snake while napping, which like a mythical Uroboros swallowed its own tail. This is how Kekule solved the puzzle of benzene molecule structure.

The existence of a causal mechanism is not the only possible physical explanation for astrology. The synchronicity principle may also play a role. Therefore, also for this reason, it is unnecessary to make the above allegations. This is of course only a hypothesis, although science knows a phenomenon that does not confirm it but at the same time, it does not deny it at all. I am talking here about a phenomenon known in quantum physics, called entanglement, which consists in the fact that the behaviour of two entangled particles is closely correlated and synchronized over time, regardless of the distance. If we assume that it is a cause-and-effect relationship, it should be objected that the speed of light is the highest speed. If it is not interrelation of the cause and effect type, then this phenomenon is the evidence of the synchronicity principle.

Types of astrological assumptions

       However, if we talk about the applicability of confirmation to astrology, it will rather be about the confirmability based on verifiability of assumptions contained in horoscopes. What kind of assumptions can they be? This topic has already been signalled when discussing the Forer effect, but I have not discussed it sufficiently. At that time, I was talking about sentences because I was referring to specific sentences from the text from the Forer experiment, but now it is more appropriate to refer to the assumptions. The difference between sentences and assumptions is that not every sentence must express some assumption, for example, interrogative or imperative sentences. In addition, one assumption may sometimes consist of more than one sentence.

I suggest that the following types of assumptions are distinguished:

  • Assumptions always true (p ˅ ¬p, i.e. p or not true that p) or very probable (each S is P).
  • Descriptive assumptions (general, imprecise). In interpretations of birth charts, these are descriptions of character traits, e.g.: “You are impulsive.” In the prognoses, these are descriptions of the nature of a given time interval or the way the owner of the horoscope experiences it, e.g.: “This year you have the chance to get rich”. The probability of their confirmation is smaller than the first type of judgments (always true) because although their meaning is quite broad it is at the same time clearly limited.
  •   Fact-based assumptions. They state unambiguous facts, veracity of which can be easily verified, e.g. in the case of birth charts it may be indication of the most likely professions performed by the owner of the horoscope, and in the case of prognostic horoscopes mentioning specific events such as illness, promotion, divorce, childbirth. These assumptions may have and usually take the form of an alternative, indicating 2 or 3 most likely events. However, it is never an alternative to expressions of opposite, mutually exclusive meanings, as in the first type of judgments: p ˅ ¬p (p or not true that p).


We already know that verifiability turned out to be an insufficient criterion. Karl Popper, however, proved confirmations useless as well. This is a criterion of gradual nature, depending on the number of experiments carried out or observations. Regardless of how many facts speak for a given theory, we can never be 100% sure. We can say even more. We are able to carry out only a finite number of experiments or observations, which in view of their potentially infinite number reduces the final quotient down to zero, and this is not too much.

Karl Popper
Karl Popper

Unlike confirmation, the Popper method gives solid results, at least in theory. This philosopher has shown that we can never be completely convinced of the truth of a given hypothesis. At the most, we can demonstrate its falsehood, or falsehood of observations that are undermining the hypothesis. This certainty results from logical rules and is therefore unchallengeable, which gives it a clear advantage over the position of the Vienna Circle.

Popper, of course, considered astrology to be a pseudo-science, because, according to him, astrology is unfalsifiable, i.e. it cannot be subjected to a trial that could undermine its statements.

Popper, however, was wrong in two ways. First of all, this philosopher apparently perceived astrology only through the prism of the first (always true or very probable) assumptions, or possibly the second type (descriptive – general, imprecise).

As for the latter, according to Popper, the assumption drawn from a horoscope that its owner will become richer in the next year would also be confirmed if he/she found 10 cents on the street. According to Popper, such judgments would be unfalsifiable and therefore unscientific.

But consider another situation. Let us use the hypothetical horoscope of an extremely calm person. After an in-depth analysis supported by consultations with other astrologers, an astrologer says that the horoscope owner is impulsive, vehement, inclined to violence, unable to self-control. Meanwhile, the person in question, being already in years but still having a good memory, does not remember to ever in his/her life behave in a manner that might confirm assumptions included in the horoscope. It means the astrologer’s thesis was wrong, which should undermine the truthfulness of the rules of astrology, i.e. falsify them.

The more so it is possible in relation to the third type assumptions, that is, the factual ones. For example, an astrologer (also after deep analyses and consultations with other astrologers) declares that in the next year the owner of the examined horoscope will divorce his wife. Meanwhile, this man, for a whole year or even two, lives with his wife in full harmony and his personal life is not disturbed at all. In this case, it would also falsify the rules of astrology.

Secondly, the principle of falsifiability is ineffective in view of all statistical rights 4, and this is the nature of astrological rules – their results are never certain, they can only be more or less likely. In other words, statistical rights, as opposed to explicit laws, are only followed up to a certain extent. Therefore, indicating cases in which statistical laws is not confirmed, does not undermine the laws as such. 5

It means that falsifiability is an inappropriate tool for assessing astrology (the probability of which is probabilistic) in terms of it being alleged or more often assumed to be a pseudo-science. I will make this statement less rigid in the future because I believe that it is possible to present astrology in a way allowing for application of the principle of falsifiability.

Astrology is one of the more popular examples of pseudo-science and the subject I discussed had also been explored by other philosophers, such as Imre Lakatos, Thomas Kuhn, Paul Feyerabend, Larry Laudan, Paul Thagard, and Michael Polanyi. This is probably because astrology clearly poses a lot of problems to those who unequivocally would like to show its pseudo-scientific character and thus the sentence uttered by Jacek Cachro, and quoted at the beginning of this text, still remains valid. It should be remembered that it is also or even above all result of a fact that the problem of demarcation, i.e. separation of science from what science is not, has not been unambiguously solved so far.

This does not mean, however, that the opposite position can be adopted, i.e. that astrology should become considered a science. And in fact, critics of astrology could basically stop there, i.e. expect from astrologers to prove, or at least to try to prove scientific nature of astrology in a relatively effective manner. So far, however, astrologers are failing in this respect.

Robert Marzewski


  • Grobler Adam: Metodologia nauk, Wyd. Aureus, Wyd. Znak, 2006, str. 312
  • Thagard Paul: Why Astrology Is a Pseudoscience, „Proceedings of the Biennial Meeting of the Philosophy of Science Association Philosophy of Science Association” 1978, no 1
  • Grobler Adam: Metodologia nauk, Wyd. Aureus, Wyd. Znak, 2006, p. 314
  • Amsterdamski Stefan: Między doświadczeniem a metafizyką, Książka i Wiedza, 1973, p. 45
  • Krajewski Władysław: Przegląd zagadnień metodologicznych i filozoficznych, Książka i Wiedza, 1998, p. 185