Robert Todd Carroll
...as above, so below...
Astrology, in its traditional form, is a type of divination based on the theory that the positions and movements of celestial bodies (stars, planets, sun, and moon) at the time of birth profoundly influence a person's life. In its psychological form, astrology is a type of New Age therapy used for self-understanding and personality analysis. (This entry concerns traditional astrology. See the entry on astrotherapy for a discussion of psychological astrology.)
The most popular form of traditional astrology is Sun Sign Astrology, the kind found in many daily newspapers which publish horoscopes. A horoscope is an astrological forecast. The term is also used to describe a map of the zodiac at the time of one's birth. The zodiac is divided into twelve zones of the sky, each named after a constellation which originally fell within its zone (Taurus, Leo, etc.). The apparent paths of the sun, the moon, and the major planets all fall within the zodiac. Because of the precession of the equinoxes, the equinox and solstice points have each moved westward about 30 degrees in the last 2,000 years. Thus the zodiacal constellations named in ancient times no longer correspond to the segments of the zodiac represented by their signs. In short, had you been born at the same time on the same day of the year 2,000 years ago, you would have been born under a different sign.
Traditional Western astrology may be divided into tropical and sidereal. (Astrologers in non-Western traditions use different systems.) The tropical, or solar, year is measured relative to the sun and is the time (365 days, 5 hr, 48 min, 46 sec of mean solar time) between successive vernal equinoxes. The sidereal year is the time (365 days, 6 hr, 9 min, 9.5 sec of mean solar time) required for the earth to complete an orbit of the sun relative to the stars. The sidereal year is longer than the tropical year because of the precession of the equinoxes, i.e., the slow westward shift of the equinoctial points along the plane of the ecliptic at a rate of 50.27 seconds of arc per year, resulting from precession of the earth's axis of rotation. Sidereal astrology uses the actual constellation in which the sun is located at the moment of birth as its basis; tropical astrology uses a 30-degree sector of the zodiac as its basis. Tropical astrology is the most popular form and it assigns its readings based on the time of the year, while generally ignoring the positions of the sun and constellations relative to each other. Sidereal astrology is used by a minority of astrologers and bases its readings on the constellations near the sun at the time of birth.
One of the common arguments in favor of astrology is the fallacious argument from popularity and tradition: astrology is believed by millions of people and it has survived for thousands of years. These claims are true, but are irrelevant to the "truth" of astrology. The ancient Chaldeans and Assyrians engaged in astrological divination some three thousand years ago. By 450 B.C.E. the Babylonians had developed the 12-sign zodiac, but it was the Greeks--from the time of Alexander the Great to their conquest by the Romans--who provided most of the fundamental elements of modern astrology.
The spread of astrological practice was arrested by the rise of Christianity, which emphasized divine intervention and free will. During the Renaissance, astrology regained popularity, in part due to rekindled interest in science and astronomy. Christian theologians, however, warred against astrology, and in 1585 Pope Sixtus V condemned it. At the same time, the work of Kepler and others undermined astrology's tenets.
Is astrology testable?
A second argument in favor of astrology is that it is testable and there is evidence that the data supports the hypothesis that there is a causal connection between heavenly bodies and human events. For example, according to the so-called Mars effect, great athletes are born not made. This claim is based on a statistical analysis of birth dates of great athletes and the position of Mars when they were born. It is said that the correlation is greater than one would expect by chance. Others disagree and claim the evidence does not show a correlation that would not be expected by chance. However, even if there were a significant correlation between the position of Mars at one's birth and one becoming an exceptional athlete, that would not imply or even indicate that there is a causal connection between the position of a planet and the kind of endeavors one is likely to be good at here on earth. Correlation between x and y is not a sufficient condition for reasonable belief that x causes y. Even a statistically significant correlation between x and y is not a sufficient condition for reasonable belief in a causal connection, much less for the belief that x causes y. Correlation does not prove causality.
Correlation may not prove causality, but it is extremely attractive to defenders of astrology. For example: "Among 3,458 soldiers, Jupiter is to be found 703 times, either rising or culminating when they were born. Chance predicts this should be 572. The odds here: one million to one." [Michel Gauquelin, "Spheres of Influence," Psychology Today (Brit.), No. 7, October 1975, pp. 22-27. Reprinted in Philosophy of Science and the Occult (Albany: State University of New York Press, 1982)]. I'm willing to assume that all the statistical data which shows a significant correlation between various planets rising, falling, culminating, or whatever else they might be seen as doing, is accurate. However, it would be more surprising if of all the billions and billions of celestial motions conceivable, there weren't a great many that could be significantly correlated with dozens of mass events or individual personality traits.
For example, defenders of astrology are fond of noting that 'the length of a woman's menstrual cycle corresponds to the phases of the moon' and 'the gravitational fields of the sun and moon are strong enough to cause the rising and falling of tides on Earth.' If the moon can affect the tides, then surely the moon can affect a person. But what is the analog to the tides in a person? We are reminded that humans begin life in an amniotic sea and the human body is 70 percent water! If oysters open and close their shells in accordance with the tides, which flow in accordance with the electromagnetic and gravitational forces of the sun and moon, and humans are full of water, then isn't it obvious that humans must be influenced by the moon as well? It may be obvious, but the evidence from moon studies does not support it.
Astrologers emphasize the importance of the positions of the sun, moon, planets, etc., at the time of birth. But why are the initial conditions more important than all subsequent conditions for one's personality and traits? Why is the moment of birth chosen as the significant moment rather than the moment of conception? Why aren't other initial conditions such as one's mother's health, the delivery place conditions, forceps, bright lights, dim room, back seat of a car, etc., more important than whether Mars is ascending, descending, culminating or fulminating? Why isn't the planet Earth, much closer to us at birth, considered a major influence on who we are and what we become?
Other than the sun and the moon and an occasional passing comet or asteroid, most planetary objects are so distant from us that any influences they might have on anything on our planet are likely to be wiped out by the influences of the sun and moon. Earth, and the people and things on earth that a person comes in direct contact with, are likely to be more important as influencing factors in our lives than distant heavenly bodies. What's more, if it turns out that we can determine specific effects from specific birthplace conditions, then we can control those conditions to bring about beneficial results. On the other hand, even if it were true that the position of the stars and planets is more important to your life than whether your birth was a difficult one under horrendous conditions, there is nothing we can do about the stars and there is a limit to how much control we can have over the time of a person's birth. (I am glad I won't be an astrologer in the age of test tube babies. How would I know when my client was 'born'? The birthing process isn't instantaneous. There is no single moment that a person is born. The fact that some official somewhere writes down a time of birth is irrelevant. Do they pick the moment the water breaks? the moment the first dilation occurs? when the first hair or toenail peeks through? when the last toenail or hair passes the last millimeter of the vagina or belly surface? when the umbilical cord is cut? when the first breath is taken? or the moment when the physician or nurse looks at a clock or watch [no doubt magically free from the possibility of inaccuracy] to note the time of birth?)
No one would claim that in order to grasp the effect of the moon on the tides or potatoes one must understand initial conditions of the Singularity before the Big Bang, or the positions of the stars and planets at the time the potato was harvested. If you want to know what tomorrow's low tide will be you do not need to know where the moon was when the first ocean or river was formed, or whether the ocean came first and then the moon, or vice-versa. Initial conditions are less important than present conditions to understanding current effects on rivers and vegetables. If this is true for the tides and plants, why wouldn't it be true for people?
correlation is not causality
This fascination with correlation is also found in the reasoning of those who try to make every ancient megalithic site into an astronomical observatory of some sort. Defenders of astrology should note what Aubrey Burl wrote of such reasoning.
Also, while it is true that the odds are inconceivably large that anyone would make more than 20 straight passes at the craps table, it's happened. Given enough craps games, the inconceivable will become the frequent. In short, what seems to defy the "laws" of statistics, may not do so when examined more carefully.
Finally, there are those who defend astrology by pointing out how accurate professional horoscopes are. A colleague of mine, a history teacher with a Ph.D. in history from the University of California at Davis, practices astrology. Of course, he's high tech and has a computer program to help him do his readings. He is aware of all the arguments against astrology and even admits that logically it shouldn't work. But it does, he believes. This concept of 'works' is intriguing. What does it mean?
Basically, to say astrology works means that there are a lot of satisfied customers. It does not mean that astrology is accurate in predicting human behavior or events to a degree significantly greater than mere chance. The main support for this argument is in the form of anecdotes and testimonials. There are many satisfied customers who believe that their horoscope accurately describes them and that their astrologer has given them good advice. Such evidence does not prove astrology so much as it demonstrates the effects of cold reading, the Forer effect, and confirmation bias. Good astrologers give good advice, but that does not validate astrology. There have been several studies which have shown that people will use selective thinking to make any chart they are given fit their preconceived notions about themselves and their charts. Many of the claims made about signs and personalities are vague and would fit many people under many different signs. Even professional astrologers, most of whom have nothing but disdain for Sun Sign Astrology, can't pick out a correct horoscope reading at better than a chance rate. Yet, astrology continues to maintain its popularity, despite the fact that there is scarcely a shred of scientific evidence in its favor. Even the First Lady of the United States, Nancy Reagan, and her husband, Ronald, consulted an astrologer while he was the leader of the free world. From which I can only conclude that astrologers have more influence than the stars do.
Is it possible that I am who I am because of the position of the planets, stars, moons, comets, asteroids, quasars, black holes, etc., at the moment of my birth? Yes, it is possible. Do I have any reason to think that this possibility is more likely than the opposite possibility, namely, that these matters are insignificant and irrelevant to my 'destiny'? No. I can't find a single good reason for believing any of this. But I am a Taurus and we all know how stubborn I should be.
See related entrieson astrotherapy and the full moon.
Culver, Roger B. and Philip A. Ianna. Astrology, True or False? : A Scientific Evaluation (Buffalo, NY: Prometheus Books, 1988).
Dean, Geoffrey and Arthur Mather and Ivan W. Kelly, "Astrology," in The Encyclopedia of the Paranormal, ed. G. Stein (Amherst, N.Y.: Prometheus Books, 1996).
Kelly, I.W. , G.A. Dean and D.H. Saklofske, "Astrology, A Critical Review," in Philosophy of Science and the Occult, 2nd ed. ed. Patrick Grim (Albany, New York: State University of New York Press, 1990), pp. 51-81.
Kelly, I.W. "Modern Astrology: A Critique," Psychological Reports, 1997, 81, 1035-1066.
Kelly, I.W. "Why Astrology Doesn't Work," Psychological Reports, 1998, 82, 527-546.
Randi, James. Flim-Flam! (Buffalo, New York: Prometheus Books,1982), chapter 4. Nature, Vol. 318 p. 419 (5 December 1985).
Robert Todd Carroll