In its modern guise, astrology is based on the assertion that the apparent positions of certain objects in the solar system at the time an individual is born are somehow correlated with his or her personality, activities, preferences and even major life events -- accidents, marriages, divorces, etc. The "stars" (usually only the sun, the earth's moon, and the five planets known in antiquity: Mercury, Venus, Mars, Jupiter and Saturn) determine the best day to ask your boss for a raise, go to the dentist, or take a laxative. There is no agreement whatsoever among astrologers as to how or why this can be. Nor is there any agreement as to precisely what planetary positions lead to which specific traits or experiences. It is almost certain that no two astrologers will "cast" the same individual's horoscope with the same -- or even a similar -- result. The descriptions and situations that do result are generally so vague that they apply to nearly everyone alive on earth at present, so that meaningful verification is an impossibility. How did such a belief get imbedded in our so-called scientific culture?
Astrology is best understood by learning how it began. Astrology is unquestionably the oldest and at the same time currently the most popular of all pseudosciences. The origins of astrology can be traced back 3,000 years, to ancient Babylonia. The existence of large cities depends on efficient and reliable agriculture, and therefore on an accurate calendar, so that farmers know when to plant, when to harvest, etc. The astronomical observations required to construct a calendar and maintain its accuracy were the task of Babylonia's priesthood. Since the observers were priests, it seems natural that their names for the objects in the sky they found most useful for calendar purposes corresponded to the names of the immortal gods in the Babylonian pantheon. We still use these god-names for the planets, although our names (Mars, Venus, Jupiter, etc.) are for the Roman counterparts of the Babylonian gods (Nergal, Ishtar, Marduk, etc.). It was not just a matter of easy-to-remember names: the planets, in some sense, were the gods they were named for.
This odd blend of astronomy and religion led, by about 1,000 BC, to an extensive literature of "planetary omens." Since Nergal (Mars) was the god of wars and bloody battle, a summer in which Nergal shown down brightly from the sky was a good time to wage war (or a time in which risk of war was great). Since Ishtar (Venus) was the goddess of sexual love, a spring night in which Ishtar hung high in the west after sunset was a good time to proposition your girlfriend, chase the new slave around the bed, etc.
By about 600 BC the Babylonians had devised the twelve-sign zodiac: markers in the sky along the ecliptic, the apparent path along which the sun, moon, and five naked-eye planets -- Mercury, Venus, Mars, Jupiter and Saturn -- move in the sky. The "horoscope," a crude chart of the positions of the planets along the zodiac at a given moment of time, was devised soon after. The oldest known horoscope was made for April 29, 410 BC. During the classical era dominated by first Greece and then Rome, Babylonian astrologers (called "Chaldeans") set up shop in most of the large urban areas throughout the civilized world. Greek astronomers scoffed at the Chaldean cults as a ludicrous combination of primitive astronomy and primitive religion, but to no avail -- the Greek and later the Roman public embraced astrology as lovingly as they embraced most of the other bizarre and barbaric cults that wandered to the Mediterranean looking for converts. That astrology makes no sense with its Babylonian religious underpinnings removed was apparent to thinking people from the very first. Roman statesman Marcus Tullius Cicero wrote, in 44 BC, a devastating critique of astrology, which is well worth reading today. Among the points made by Cicero was that no one sees or expects any correlation between the weather conditions at the time of birth of a child and the child's later personality or fortunes. Yet clearly the weather -- extreme cold or heavy rain or harsh heat -- has far more effect on a living thing than dim lights in the night sky. And even if all children born in December were similar in some way -- which they are not -- how would an astrologer know that these similarities were not due to the weather, due to all the children being born into a cold environment, rather than to the sun being in "Sagittarius," or whatever?
However, with the coming of Christianity, the Chaldeans indeed had very hard going. During the early Middle Ages, astrology became essentially extinct in Europe, though kept alive by Islamic scholars. The Crusades brought the heritage of Greek and Roman culture back to Europe and astrology tagged along, co-existing uneasily with Christianity until the dawn of the age of science. The explosive growth of scientific astronomy from 1600 AD onward paralleled a steady decline in the public interest in astrology. By the end of the 19th Century, a French encyclopedia could accurately describe astrology as a vanishing cult with no young adherents.
But astrology made its strongest comeback in all of history in the early 1930s when British astrologer R. H. Naylor invented the daily newspaper horoscope column. Soon every newspaper had such a column and every town several practicing astrologers. The paradoxical result is that the heyday of astrology was not during the benighted Middle Ages, when the average person was sunk deep in ignorance and superstition, and kept there by illiteracy and the rarity of books. Rather, astrology's peak popularity comes at a time when most citizens presumably know the basic facts of astronomy, and are well aware from space-probe photos in the daily newspapers and on TV that the other planets are worlds more or less similar to the earth, and not mystical god-fires in the sky.
At the present time, at least 90% of all Americans under 30 are said to know their "sun-sign." How many know their blood type? Or the name of the Secretary of State? Or Newton's Three Laws of Motion?
Scientists have been quite baffled by the popularity of astrology during the 20th Century, and dozens of careful studies have been carried out to see if there is any actual correlation between the positions of the planets at an individual's birth, and any attribute of the individual in later life. NO statistically valid study has ever shown ANY connection, relation or correlation that would give ANY support to ANY part of astrology. There is no scientific question, there is no scientific controversy, concerning astrology -- it definitely does NOT work.
Why, then, is astrology the most popular of all the pseudosciences? Before turning to this question, let us look more closely at the actual procedures by which the dogmas of astrology generate individual predictions. In order to go from an individual's horoscope, which strictly speaking is just a crude chart of the heavens at the time of the individual's birth, to specific predictions or statements about the individual, the astrologer must consult a table. This table says something like, "Sun in Pisces at birth = individual is a good dancer, has strong feminine characteristics," etc., etc., etc. Now, where did this table come from? (Note that is such a table, not the horoscope itself, or the procedures for drawing the horoscope chart, that is the "guts" of astrology.) The answer is that such tables are simply made up, up whoever wrote the particular manual of astrology being used! This is why two different astrologers will rarely, if ever, "read" the same horoscope the same way. Of course, there are traditional tables, but wherever the table comes from, it is an arbitrary matching of horoscope features to individual characteristics. The predictions are generated randomly, as much as if by throwing dice.
This kind of arbitrariness is characteristic of all pseudosciences, not just astrology. It comes about because the origins of pseudosciences lie not in observations of nature, which anyone can make, and which are "universal" in character -- rather, they lie in accidental historical conventions and cultural traditions. The ancients happened to call the second planet from the sun Venus and the fifth planet from the sun Jupiter. Had they done it just the other way, it would not have made the slightest difference to astronomy, which is concerned with reality -- with the planet itself. Venus would be the big colorfully belted planet with a red spot and many moons. Jupiter would be the nearest planet to earth, hellishly hot. The names would be different, but nothing else, since the names are arbitrary anyway. We could call them "Two" and "Five" if we didn't want to keep the Babylonian-Greek-Roman tradition of gods' names. But note that changing the names would make astrology totally different, because astrology depends only on the names. The "lookup tables" used by astrologers are generally based entirely on word association and suggestions from the names of the things in the horoscope. Thus, Jupiter, chief of the gods, is a leader among gods and men. Venus, goddess of love, rules the emotions. And so on.
Another amusing way to see this arbitrariness is to consider the zodiac, the named divisions of the ecliptic. The Babylonian astrologers, with their heritage of worrying about calendars, sometimes used 12 zodiac signs. But there is no reason for any particular number. The Chinese and Hindus had 28. The Toltec cultures of Middle America had 20. The Babylonians themselves used anywhere from 6 to 18 at various times. The arbitrariness of numbers of signs -- not to mention names of signs -- is obvious. If a given group of stars (unrelated except by the common name!) was given the name "Aries the Ram," this arbitrarily assigned name then predetermines the most popular "interpretations" that are the basis of the tables that astrologers must have for since rams are aggressive and assertive (in folklore anyway), so will be people born with the sun (or something) "in Aries." How one would distinguish the aggressiveness of the ram from that of the goat Capricorn or the scorpion Scorpio is another problem!