The fundamental notion underlying astrology is that the heavenly bodies control,influence or predict what happens on earth. This belief goes back to the very earliest ages of humanity, and it is easy to understand why it arose. Our remote ancestors observed the endless turning of the heavens, where different constellations of the stars were visible at different times of the year, the phases of the moon, the rising of the sun in the heavens in spring and its falling in autumn; and they would have wondered why these happened. They would also have noticed that there were certain heavenly bodies which looked like stars but behaved quite differently, for they moved about in a strange way; sometimes reversing, sometimes disappearing for months at a time. The Greeks called them "planets": this is, "wanderers". There were five of them: we call them Mercury, Venus, Mars, Jupiter and Saturn (the outer planets are too faint to be seen with the naked eye), and they were identified with gods. Early observers would also have noticed that these planets were only to be seen in a certain belt of constellations, which also happened to be the path with the sun and moon followed across the sky. These constellations are called the zodiac. To put this in simple terms: the most readily identifiable constellation is Orion, which dominates the southern sky in winter, though it cannot be seen in summer. The sun and moon follow a path just above Orion, through the constellations of Gemini (above and a little to the left) and Taurus (above and a little to the right). Planets may be seen along this same path, but not anywhere else. The five planets, plus the sun and to moon, give us the total of seven, whence come the seven days of the week. In addition, there were such occasional alarming phenomena as eclipses, comets and showers of meteorites.
To our ancestors, none of this could be accidental, or have no relevance to us: it must be the gods sending us messages, if only we had the knowledge to interpret them. Astrology goes back at least to ancient Babylon, it fascinated the Romans, and gained new life in the Renaissance when, under the influence of Neoplatonism, it was believed that everything in the universe was closely connected in a vast network of mutual influences. Monarchs and even Popes had their horoscopes cast, and the finest mathematicians of the age used their skill to cast them. However, astrology soon came under attack from two different directions. In the great witch-hunt of the 16th and 17th centuries it was denounced as forbidden knowledge; and in the rising movement of scientific thought it was condemned as not knowledge at all, just rubbish. Since the 18th century it is difficult to find anyone of high intelligence who believed in astrology.
Why can't astrology be regarded as a science?
Scientific knowledge involves first and foremost the accumulation of data, and the formulation of hypotheses that attempt to explain the data. All scientific "laws" are in fact theories, and if new and puzzling data appear, then the theories may need to be modified. Astrology is not like this. There is absolutely no reason to believe that the astrological impact of the constellations and planets was based upon centuries of observation; nor were the ideas ever modified. To take an example, when the planet Uranus was discovered in the 18th century, followed by Neptune in the 19th, did astrologers seize on this and say, "Ah! perhaps these discoveries explain certain strange anomalies in our calculations!", and then spend many years gathering evidence as to the likely influence of these newly-discovered planets? Of course they didn't! And what was the astrological impact of Pluto being discovered as a new planet in the 20th century, and then, more recently, degraded from planetary status? We still await a verdict.
Astrologers have never attempted to investigate or explain the forces behind astrology. Either the patterns seen in the heavens are messages from the gods, or they exert some influence of their own. Which is it? If it is the latter, then some kind of force is being exerted. Let us call it "astrological force". What is its nature? Has it ever been investigated? It is clearly a very strange force, in that a planet can be said to be increasingly influential astrologically despite the fact that, in astronomical terms, it may be moving away from us! All this might have made sense in the Ptolemaic model of the universe, which placed the earth at the centre, but it makes no sense in the Copernican model, with the sun at the centre and the stars inconceivably distant.
Astrologers make two claims which, though not actually contradictory, are quite different. The first is that our personalities are determined by the pattern of the heavens at the time of our birth. The second is that examining the heavens will enable us to anticipate coming events. Let's examine the first claim. To throw out suggestions at random: are you more likely to be an optimist if born under Leo? To be a creative artist if born under Gemini? Or to have sporting talent if born under Aquarius? Do family, educational and social factors count for nothing? In any case, how were these predictions arrived at? Was it by many generations of careful observation, and modified where necessary? This seems extremely unlikely. Then again, why should the moment of birth be the deciding factor? In the 18th century it was sometimes considered that the moment of conception was more important. (This is why, in Laurence Sterne's novel "Tristram Shandy" the central character has such a confused life: it is because his mother, at that vital moment, asked his father whether he had remembered to wind up the clock! It is also why the radical troublemaker John Wilkes told a silly nobleman who had been born on January 1st that he was obviously conceived on April Fools' Day!). Have astrologers investigated and discarded this theory? Or what about a totally different, and randomly chosen theory; namely that personality is determined by the weather at the time of birth? Has this been investigated?
The second claim is that the heavenly bodies afford some prediction of the future. This will involve a philosophical debate concerning inevitability, or fate, as well as the problem of "astrological force" as mentioned above. But there is another problem implicit in this; namely, that almost all events affect several people.
Think of the following scenario. The footballer Wayne Rooney is injured, and a medical investigation rules him out of a vital international match. Rooney's horoscope should therefore tell him that he will receive bad news. But there is more to it than this. Suppose a young player (let's call him Fred Smith) is called up for his first international appearance to replace Rooney. Smith's horoscope should tell him that someone else's misfortune will work to his advantage. The rest of the England team, the manager and countless supporters will have been alarmed by Rooney's injury; but let's suppose that Smith plays extremely well and England win. All these other people (who will have a variety of star-signs) should therefore be told that they will receive some alarming news, but that it all turns out for the best. Should we anticipate this from the astrologers? What do you think?
My final point is a personal one. I was born on February 18th, and was always told this placed me under Aquarius, but now according to some astrologers this date is under Pisces. Indeed, in one paper just last week there were two sets of astrological predictions, one of which put my date under Aquarius and the other under Pisces! Come on, astrologers! Get your act together!