Is Astrology a Pseudoscience?
Examining the Basis and Nature of Astrology
If astrology is not really a science, then is it possible to classify it as a form of pseudoscience? Most skeptics will readily agree with that classification, but only by examining astrology in light of some basic characteristics of science can we decide if such a judgment is warranted. First, let's consider eight basic qualities which characterize scientific theories and which are mostly or entirely lacking in pseudoscience:
Consistent (internally and externally)
Parsimonious (sparing in proposed entities or explanations)
Useful (describes and explains observed phenomena)
Empirically Testable & Falsifiable
Based upon Controlled, Repeated Experiments
Correctable & Dynamic (changes are made as new data is discovered)
Progressive (achieves all that previous theories have and more)
Tentative (admits that it might not be correct rather than asserting certainty)
Just how well does astrology stack up when measured against these standards?
Is Astrology Consistent?
To qualify as a scientific theory, an idea has to be logically consistent, both internally (all of its claims must be consistent with each other) and externally (unless there are good reasons, it must be consistent with theories which are already known to be valid and true). If an idea is inconsistent, it is difficult to see how it actually explains anything at all, much less how it could possibly be true.
Astrology, unfortunately, cannot be called consistent either internally or externally. Demonstrating that astrology is not consistent externally with theories known to be true is easy because so much of what is claimed about astrology contradicts what is known in physics. This wouldn't be such a problem if astrologers could demonstrate that their theories explain nature better than much of modern physics, but they can't - as a consequence, their claims cannot be accepted.
The degree to which astrology is internally consistent is more difficult to say because so much of what is claimed in astrology can be very vague. It is certainly true that astrologers themselves regularly contradict each other and that there are different forms of astrology which are mutually exclusive - thus, in that sense, astrology is not internally consistent.
Is Astrology Parsimonious?
The term "parsimonious" means "sparing or frugal." In science, to say that theories must be parsimonious means that they should not postulate any entities or forces which are not necessary to explain the phenomena in question. Thus, the theory that little fairies carry electricity from the light switch to the light bulb is not parsimonious because it postulates little fairies which simply aren't necessary to explain the fact that, when the switch is hit, the bulb comes on.
Likewise, astrology is also not parsimonious because it postulates unnecessary forces. For astrology to be valid and true, there must be some force which establishes a connection between people and various bodies in space. It is clear that this force cannot be anything already established, like gravity or light, so it must be something else. However, not only are astrologers unable to explain what his force is or how it operates, but it isn't necessary to explain the results which astrologers report. Those results can be explained much more simply and readily through other means, such as the Barnum Effect and Cold Reading.
For astrology to be parsimonious, the astrologers would have to produce results and data which cannot readily be explained by any other means but a new and undiscovered force which is capable of creating a connection between an individual and bodies in space, of influencing a person's life, and which is dependent upon the exact moment of his or her birth. However, despite the millennia which astrologers have had to work on this problem, nothing has been forthcoming.
Is Astrology Based Upon Evidence?
In science, the claims made are verifiable in principle and then, when it comes to experiments, in fact. In pseudoscience, there are extraordinary claims made for which incredibly insufficient evidence is provided. This is important for obvious reasons - if a theory is not based upon evidence and cannot be empirically verified, there is no way to claim that it has any connection with reality.
Carl Sagan coined the phrase that "extraordinary claims require extraordinary evidence." What this means in practice is that if a claim is not very strange or extraordinary when compared to what we already know about the world, then not a lot of evidence is needed in order to accept the claim as likely to be accurate.
On the other hand, when a claim very specifically contradicts things which we already know about the world, then we would need quite a lot of evidence in order to accept it. Why? Because if this claim is accurate, then a lot of other beliefs which we take for granted cannot be accurate. If those beliefs are well-supported by experiments and observation, then the new and contradictory claim qualifies as "extraordinary" and should only be accepted when the evidence for it outweighs the evidence we currently possess against it.
Astrology is a perfect example of a field characterized by extraordinary claims. If distant objects in space are able to influence the character and lives of human beings to the degree alleged, then fundamental principles of physics, biology and chemistry which we already take for granted cannot be accurate. This would be extraordinary. Therefore, quite a lot of very high-quality evidence is required before the claims of astrology could possibly be accepted. The lack of such evidence, even after millennia of research, indicates that the field is not a science but rather a pseudoscience.
Is Astrology Falsifiable?
Scientific theories are falsifiable, and one of the characteristics of pseudoscience is that pseudoscientific theories are not falsifiable, either in principle or in fact. To be falsifiable means that there must exist some state of affairs which, if it were true, would require that the theory is false.
Scientific experiments are designed to test for exactly such a state of affairs - if it occurs, then the theory is false. If it doesn't, then the possibility that the theory is true is made stronger. Indeed, it is a mark of genuine science that practitioners seek out such falsifiable conditions while pseudoscientists ignore or avoid them entirely.
In astrology, there does not appear to be any such state of affairs - that would mean that astrology is not falsifiable. In practice, we find that astrologers will latch onto even the weakest sorts of evidence in order to support their claims; however, their repeated failures to find evidence are never allowed as evidence against their theories.
It is certainly true that individual scientists can also be found avoiding such data - it is simply human nature to want a theory to be true and to avoid conflicting information. However, the same cannot be said for entire fields in science. Even if one person avoids unpleasant data, another researcher can make a name for herself by finding and publishing it - this is why science is self-correcting. Unfortunately, we don't find it occurring in astrology and because of that, astrologers cannot claim that astrology is consistent with reality.
Is astrology based upon controlled, repeatable experiments?
Scientific theories are based upon and lead to controlled, repeatable experiments, whereas pseudoscientific theories are based upon and lead to experiments which are not controlled and/or are not repeatable. These are two key characteristics of genuine science: controls and repeatability.
Controls means that it is possible, both in theory and in practice, to eliminate possible factors which might be affecting the results. As more and more possible factors are eliminated, it is easier to claim that only one particular thing is the "real" cause of what we see. For example, if doctors think that drinking wine makes people healthier, they will give test subjects not simply the wine, but drinks which contain only certain ingredients from the wine - seeing which subjects are healthiest will indicate what, if anything, in the wine is responsible.
Repeatability means that we are cannot be the only ones who arrive at our results. In principle, it must be possible for any other independent researcher to try to perform the exact same experiment and arrive at the exact same conclusions. When this happens in practice, our theory and our results are further confirmed.
In astrology, however, neither controls nor repeatability appear to be common - or, sometimes, to even exist at all. Controls, when they do appear, are typically very lax. When controls are sufficiently tightened to pass regular scientific scrutiny, it is common that astrologers' abilities no longer manifest themselves to any degree beyond that of chance.
Repeatability also does not really occur because independent investigators are unable to duplicate the alleged findings of astrology believers. Even other astrologers prove unable to consistently replicate the findings of their colleagues, at least when strict controls on the studies are imposed. So long as the findings of astrologers cannot be reliably reproduced, astrologers cannot claim that their findings are consistent with reality, that their methods are valid or that astrology is in anyway true.
Is Astrology Correctable?
In science, theories are dynamic - this means that they are susceptible to correction due to new information, either from experiments done for the theory in question or done in other fields. In a pseudoscience, little ever changes. New discoveries and new data do not cause believers to reconsider fundamental assumptions or premises.
Is astrology correctable and dynamic? There is precious little evidence of astrologers making any basic shifts in how they approach their subject. They may incorporate some new data, like the discovery of new planets, but the principles of sympathetic magic still form the basis of everything astrologers do. The characteristics of the various zodiac signs are fundamentally unchanged from the days of ancient Greece and Babylon. Even in the case of new planets, no astrologers have come forward to admit that earlier horoscopes were all flawed due to insufficient data (because the earlier astrologers were not taking one-third of the planets in this solar system into account).
When ancient astrologers saw the planet Mars, it appeared red - this was associated with blood and war. Thus, the planet itself was associated with warlike and aggressive character traits, something which has continued down to this day. A genuine science would have only attributed such characteristics to Mars after careful study and mountains of empirical, repeatable evidence. The basic text for astrology is Ptolemy's Tetrabiblios, written about 1,000 years ago. What science class uses an 1,000 year-old text?
Is Astrology Tentative?
In genuine science, no one argues that a lack of alternative explanations is itself a reason to consider their theories correct and accurate. In pseudoscience, such arguments are made all of the time. This is an important difference because, when properly performed, science always acknowledges that the current failure to find alternatives does not indicate that a theory in question is actually true. At most, the theory should only be regarded as the best available explanation - something to be quickly discarded at the earliest possible moment, namely when research provides a better theory.
In astrology, however, claims are often framed in an unusually negative manner. The aim of experiments is not to find data which a theory can explain; instead, the aim of experiments is to find data which cannot be explained. The conclusion is then drawn that, in the absence of any scientific explanation, the results must be attributed to something supernatural or spiritual.
Such arguments are not only self-defeating but specifically unscientific. They are self-defeating because the they define the realm of astrology in narrow terms - astrology describes whatever regular science cannot, and only that much. So long as regular science expands what it can explain, astrology will occupy a smaller and smaller realm, until it finally disappears.
Such arguments are also unscientific because they move in the exact opposite direction of how science operates. Scientific theories are designed to incorporate more and more data - scientists prefer fewer theories which describe more phenomena rather than many theories which each describe very little. The most successful scientific theories of the 20th century were simple mathematical formulas which describes wide ranging physical phenomena. Astrology, however, in defining itself in narrow terms as to what cannot otherwise be explained does just the opposite.
This particular characteristic is not as strong with astrology as with other beliefs such as parapsychology. Astrology does exhibit it to some degree: for example, when it is alleged that a statistical correlation between some astronomical event and human personalities cannot be explained by any normal scientific means, therefore astrology must be true. This is an argument from ignorance and a consequence of the fact that astrologers, despite millennia of work, have so far been unable to identify any mechanism by which its claims could be caused.-->