The case for and against astrology
"If I doubt astrology to a believer, I am looked at with a shocked and bewildered stare, as if I were attacking apple pie and motherhood." Anthony Standen, Forget Your Sun Sign, 1977.
Abstract -- Eleven representative views of astrologers 1863-2006 imply that astrology is all-revealing, factual, inarguably true, applicable to everything including past lives, enthralling to thinkers, soon to dominate scientific thought, the key to a new world view, and more. Just study it seriously, they say, and you will be convinced it works. But seven representative views of scientists 1930-1998 who studied it seriously imply the exact opposite. This conflict of views can be explained by differences in what astrology means to different people, by differences in what astrology claims, and by the failure of astrologers to allow for non-astrological factors (hidden persuaders) that lead to astrology-like outcomes. The case against astrology is that it is untrue, it has failed hundreds of tests, and astrologers do not usefully agree on what a given birth chart indicates. The case for astrology is that a warm and sympathetic astrologer provides low-cost non-threatening therapy that is otherwise hard to come by. Much the same applies to sun sign astrology but at a more basic level. In short, there is more to astrology than being true or false. But astrology is an easy target for commercial abuse. It also faces strong competition from hundreds of self-help psychology books that it may or may not survive once its true nature becomes more widely known. Includes tests of validity and agreement, and insights into how not to test astrology.
End of a shouting match
Not any more. Advances in related areas (astronomy, psychology, statistics, research design) and a decisive technology (personal computers) have since 1975 put astrology under the scientific microscope like never before. Today, most questions can be answered. Quarrelling is no longer the option it once was. In what follows we ignore the usual tired arguments against astrology (sun signs do not agree with the constellations, there is no known way it could work) in favour of the only question that matters: What is the case for and against astrology?
Unfortunately the media generally see astrology only as a sales gimmick (eg sun signs in Sunday supplements) or as a source of sensation, as when phoneline astrologers earn huge sums or when crooked astrologers fleece the public. If your knowledge of astrology comes from what you read in the media, be aware that you are likely to be seriously misinformed both for and against astrology.
Views of astrologers
"Practical experiment will soon convince the most sceptical that the bodies of the solar system indicate, if they do not actually produce, changes in: 1. Our minds. 2. Our feelings and emotions. 3. Our physical bodies. 4. Our external affairs and relationships with the world at large." (Charles Carter, leading British astrologer of his day, The Principles of Astrology 1925.)
"Official science will recognise that the ancients were not mistaken, and astrology, aided by new methods of investigation, will recover its ancient prestige." (French astrologer Paul Choisnard, whose verdict was based on his experimental tests, Les Objections contre L'Astrologie: Reponses aux critiques anciennes et modernes 1929.)
"No one has ever been known to make a serious study of Astrology and then reject it." (Nicholas de Vore, American astrologer and president of the Astrologic Research Society, Encyclopedia of Astrology 1947.)
"From being an outcast from the fraternity of sciences, it seems destined to assume an almost central role in scientific thought." (John Addey, leading British astrologer of his day, Astrology Reborn 1971.)
"Astrology throws light on every department of life; ... From sex to career to character and future prospects -- and more." (American astrologer Sydney Omarr, whose astrology columns were then appearing in nearly 300 newspapers, Astrology's Revelations About You 1973.)
"There is no area of human existence to which astrology cannot be applied." (Julia and Derek Parker, The Compleat Astrologer 1975, which sold over a million copies in ten languages. The first is a former President of the British Faculty of Astrological Studies.)
"Anyone who makes a serious and open-minded study of astrology becomes totally unable to scoff. Its truths are inarguable." (Mary Coleman, Australian psychologist and astrologer, Astro-Pick your Perfect Partner 1986.)
Astrology "despite the contemptuous guffaws of scientific orthodoxy, still continues to enthral the minds of some of our finest contemporary thinkers." (Charles and Suzi Harvey, respectively former President of the British Astrological Association and former Editor of its journal, Principles of Astrology 1999.)
"Astrology's symbols are the soul's language of life. They reveal not only the mysteries of the universe but also the mysteries of each of our lives." (Gina Lake, American counselling psychologist and astrologer, Symbols of the Soul: Discovering your Karma through Astrology 2000.)
Astrology "promises to contribute to the emergence of a new, genuinely integral world view, one that ... can reunite the human and the cosmic, and restore transcendent meaning to both" (Professor Richard Tarnas, American philosopher and astrologer, Cosmos and Psyche 2006.)
In short, astrology is all-revealing, factual, inarguably true, applicable to everything including past lives, enthralling to thinkers, soon to dominate scientific thought, the key to a new world view, and more. Just study it seriously and you will be convinced it works. Or so astrologers lead us to believe. Now a word from scientists who have studied it seriously.
Views of scientists
"The ancients were evidently unaware that [astrological judgements] were the result of reasoning by analogy, which so often proves a treacherous foundation. That is why the whole superstructure of astrology is so utterly worthless and fallacious." (August Thomen, Doctors Don't Believe It 1938, a survey of medical superstitions.)
"The casting of horoscopes provides a living to thousands of individuals and provides dreams to an infinitely larger number of consumers. ... [But] since the most painstaking studies have shown the inanity of horoscopes, there should be a strong rising up against this exploitation of public credulity" (Michel Gauquelin, after analysing the horoscopes of 16,000 famous people, Dreams and Illusions of Astrology 1969.)
"The picture emerging suggests that astrology works, but seldom in the way or to the extent that it is said to work." (Geoffrey Dean and Arthur Mather, Recent Advances in Natal Astrology 1977, a critical review by fifty astrologers and scientists of over 1000 astrology books, 410 journal articles, and 300 relevant scientific works.)
"We are convinced however that astrology does not work. Astrology cannot be used to predict events of any kind, nor is astrology able to provide any useful information regarding personality, occupation, health, or any other human attribute" (Roger Culver and Philip Ianna, The Gemini Syndrome 1979, a review by astronomers of years of data collection, tests, and most of the available evidence.)
"Astrology is largely (but not entirely) superstition. However, because of the important areas which remain to be investigated, this conclusion may need future qualification. We should not be dogmatic." (Hans Eysenck and David Nias, Astrology: Science or Superstition? 1982, a review by psychologists of the then most recent research.)
"The single fact that astrologers contradict each other at about every point, and the firm convictions of their own correctness supported by their experience, must call up doubts about the reliability of [their] methods. ... Not a single classical astrological element is shown to be able to resist statistical research." (Ronnie Martens and Tim Trachet, Making Sense of Astrology 1998, a review of astrological claims.)
Evidently astrology works if studied by astrologers but not if studied by scientists. How is such disagreement possible? To find out we must first look at what is meant by "astrology".
What is meant by "astrology"?
Level of interest
On going through the levels there is a huge falling off in numbers and a dramatic change in what astrology means. At the first level are the readers of sun sign columns. They see astrology as entertainment. At the second level are those who have their birth chart calculated and read. They see astrology as an intriguing way of exploring themselves. At the third level are those who read charts to find meaning in their lives. They see astrology as a form of religion unconnected with the entertainment of sun sign columns. At the fourth level are those who test astrology scientifically. They see astrology as a popular belief worthy of study regardless of whether the belief is actually true.
The previous views of astrology by astrologers apply to levels 2 and 3, which also apply to people who consult astrologers. In the USA roughly one million people a year consult astrologers, which seems like a convincing vote in favour of levels 2 and 3. But even this number is only about 2% of the millions of Americans who at any one time are seeking answers to their psychological problems, and is less than 1% of those who read newspaper horoscopes. So the popularity of astrological consultations is perhaps no more remarkable than the popularity of any of 99 flavours of ice cream -- if it exists then some people will try it. Which of course does not explain why astrologers are convinced that astrology at levels 2 and 3 really works. For this we need to put astrology to the test.
Putting astrology to the test
Take sets of birth charts jumbled up with descriptions of their owners. Can astrologers match charts to owners? In astrology books they do it all the time. So we expect the proportion of successful matches to pile up close to 100%. To date a total of 54 studies have made this test using a total of 742 astrologers and 1407 birth charts. Despite these impressive numbers the average success rate was no different from the 50% expected by chance, see figure below. For these astrologers (many of them among the world's best) astrology performed no better than tossing a coin.
Here the results expected by chance were determined by picking matches at random for each of the 54 studies and repeating 10,000 times. The difference between the 51.7% success rate achieved by astrologers and the 50.0% expected by chance is easily explained by the tendency of journals to accept positive results and reject negative results, and is in any case not even weakly significant (p=0.77).
For astrologers this is bad news, which they dismiss in various ways. They say the tests were unduly difficult or were run by people ignorant of astrology (in fact many were run by astrologers). They say you cannot test astrology (which if true would mean they could never know anything about it). Or they see the bad news as proof of astrology's subtlety, so it is right even when it is wrong (ditto). But once again research comes to the rescue with an ingenious test that avoids any need to match charts with owners.
How well do astrologers agree on what a given birth chart indicates? To date a total of 28 studies have put this to the test using a total of 559 astrologers and 762 birth charts. Typically each test looked at how well 5 to 30 astrologers agreed on what a given chart indicated about its owner. Their average agreement was dismal -- better than tossing a coin but nowhere near the minimum acceptable, see figure below. Again many of these astrologers were among the world's best.
In general no test of individuals is acceptable unless the agreement between practitioners or between applications is above 90% where chance agreement is 50%, that is, where first and second opinions agree better than chance in 4 out of 5 cases. However, if we are interested only in large differences rather than small ones, as in measuring blood pressure, then agreement down to 75% may be acceptable provided nothing better is available elsewhere. But anything below 70% is generally useless because first and second opinions will agree better than chance in less than 2 out of 5 cases. The average agreement among astrologers was 54.9%, or better than chance in barely 1 out of 10 cases.
The next question is obvious. If astrologers cannot usefully agree on what a birth chart indicates, how can they know that astrology works? Indeed, why should anyone bother with astrology in the first place? It is here that we need to ask what is meant by "astrology works".
What is meant by "astrology works"?
At one extreme are people who seek only personal meaning. For them astrology works if it provides meaning. Here "it works" means "it is meaningful." This kind of astrology does not need to be true, and attacking it would be like attacking Superman comics or a religious faith. At the other extreme are people who seek only factual proof. For them astrology needs to be true. Here "it works" means "it delivers results beyond those explained by non-astrological factors", of which more later.
In between are people who see astrology as meaningful but grounded in the kind of factual statements ("Leos are generous") that fill astrology books. This allows research findings to be welcomed if positive ("it confirms astrology!") and rejected if negative ("astrology is not like that!"). But it does not end there.
How to convince yourself that astrology works
Still cautious, you have your birth chart read. The astrologer tells you things she could not possibly have known, like you have a sense of humour and you sometimes worry about money. Amazingly, everything fits. You are now convinced that astrology works. You haven't the foggiest idea how it works but it certainly works. You conclude that disbelievers have no idea what they are talking about.
For astrologers that is the end of it. Millions of people have tested astrology in this way, and millions have ended up convinced that it works. For them this is end of story. Astrology really works! No doubt about it!
Why scientists are not convinced
The results confirm their suspicions. Whereas 90% of Leos said they were like Leo, so did 90% of non-Leos. Absence of a Mars-Neptune conjunction made no difference to people's idealism. And someone else's chart fitted them just as well as their own -- a point repeatedly confirmed by astrologers whenever they inadvertently use the wrong chart. Many tests with switched data have been made, always with results like these. Which of course is consistent with the studies shown earlier, where astrology performed no better than tossing a coin, and astrologers failed to usefully agree on what a given chart indicated.
For scientists that is the end of it, at least until the evidence indicates otherwise. Your sun sign and birth chart may fit you exactly but so do sun signs and birth charts not your own. Astrologers and clients cannot tell the difference. Like the Emperor's New Clothes, astrology seems to be built on self-deception. At which point the message is clear.
The message is clear
The case against astrology
But the claim that astrologers repeatedly make (astrology is true because based on experience) is simply mistaken -- what they see as its strength (experience) is actually its weakness (the experience is not assessed using switched data). They show little awareness of the factors such as the absence of accurate feedback that prevent learning from experience, or of the numerous hidden persuaders that give the illusion of such learning in its absence. Astrologers also show little interest in procedures that avoid the weaknesses of experience, and every interest in ignoring unwelcome evidence. Together these attitudes have created a case against that is longer and stronger than the case for.
The case for astrology
Much the same applies to sun sign astrology but at a more basic level -- and many people seem to want it. Or as historian and social critic Theodore Roszak says in his book Why Astrology Endures (Briggs, San Francisco 1980): "For a growing number of people, the rich imagery of these old traditions has become a more inspirational way of talking [about ourselves] ... than conventional psychiatry. The astrological universe is, after all, the universe of Greco-Roman myth, of Dante, Chaucer, Shakespeare, Milton, Blake. It has poetry and philosophy built into it."
You can find more on tests of astrology in Research results, which gives abstracts for 91 studies typical of those made in the 1980s and 1990s, and in Meta-analyses, which gives overviews of all studies made in particular areas. Both articles are on this website under Doing Scientific Research.