What is astrology

Astrology is the reading of correspondences between the positions of the planets and human experience. It starts from a piece of astronomical arithmetic — where each body stood at one moment — and proposes a meaning for that arrangement.

There are two halves, and confusing them is the origin of almost every argument on the subject. The first half is calculation, and it can be checked: the position of Mars on the third of March 1988 is the same for whoever calculates it, from tables published since the nineteenth century. The second is interpretation, and it is a tradition of reading built, argued over and rewritten across twenty-four centuries.

What it delivers to a person is vocabulary. A chart tells no news about anybody: it names what the person already lives and had no words for, and shows that the thing has a shape, a counterpart and a use. That is why a good reading tends to be recognised before it is learned.

What an astrologer actually does

They calculate a chart and read it in layers, from the heaviest piece to the lightest. The work has four steps, and none of them is memorising sign meanings.

• Calculates. Date, time and city become a birth chart: ten planets, twelve houses and the angles between them.
• Looks for what repeats. The subject of a chart is whatever shows up three times by different routes — a planet, the house it sits in and the ruler of that house all saying the same thing.
• Weighs. Sun, Moon and Ascendant weigh more than Neptune in the eleventh house. A reading that treats the eleven pieces as equals is a list, and a list is not a reading.
• Translates. The last stage is the only one the client cares about: saying all of it in the language of that person's life, with examples they recognise in their own week.

The hard part is the third. Every chart has material to say anything at all if you cherry-pick what to quote — and that is exactly where astrology turns into fortune-telling. Hierarchy is what stops it.

Where astrology came from

It began by looking at the State, and not at persons. In Mesopotamia, scribes recorded celestial omens concerning the king, the harvest and the war. The fate of an individual was no business of the sky.

It was in Babylon, in the fifth century before Christ, that the band the planets travel through was cut into twelve equal slices of thirty degrees, named after the constellations occupying each stretch at the time. And the oldest known birth chart dates from 29 April 410 before Christ : a clay tablet with the positions calculated for a child, and it marks the turn where the sky became the business of one private life.

In the second century after Christ, in Alexandria, Claudius Ptolemy wrote the manuals for both. The Almagest was the astronomy book of the West for fourteen hundred years; the Tetrabiblos organised astrology and fixed the convention it still uses, that of beginning the zodiac at the point of the March equinox.

For more than a thousand years the two were a single profession. Astrology was a university subject in Europe, physicians consulted the sky before a bleeding, and Johannes Kepler — the man who discovered that orbits are ellipses — earned part of his living calculating charts and wrote a treatise in 1601 proposing firmer foundations for astrology. The parting of the two dates from the seventeenth century onwards, and has a story of its own.

Between Ptolemy and medieval Europe there is a bridge almost nobody mentions: the translators and astronomers of the Islamic world, who kept, corrected and expanded that material between the eighth and twelfth centuries, and through whom it returned to the West in Latin. The Arabic name of dozens of stars astronomy still uses is the trace of that passage.

The format most people know today is the newest of all: the column of twelve paragraphs by date of birth is less than a hundred years old, and was born in an English newspaper in 1930.

What astrology is not

It is not tarot and it is not numerology. They are three systems of different origins that meet only on the shelves of the same shop. Tarot reads cards drawn now; numerology works with numbers from a name and a date; astrology starts from calculated astronomical positions. Anyone mixing the three into one text is talking about something else.

Nor is it a single thing. Western astrology measures the zodiac from the March equinox; the Vedic one, called jyotish, pins it to the stars. Since the equinox point drifts about one degree every 72 years, today there are almost 24 degrees between the two rulers — enough for most people to hold, in the Vedic system, the sign before the one they know. Neither got the arithmetic wrong: they measure from different starting points, on purpose.

And it is not the newspaper horoscope. That one divides the world into twelve bands and speaks to everyone in a band at once, because it was invented to fit a newspaper page. A chart belongs to one person.

Is astrology a science, then?

No, and it does not need to present itself as one. Science is a method: hypothesis, a prediction that can fail, an experiment that decides. Astrology is not organised that way, and the controlled tests that tried to measure an astrological effect did not find what they were looking for.

Writing this on a page that sells astrological readings looks like working against my own interest, and it is the opposite. Whoever promises science where there is none delivers superstition in a lab coat, and it is that promise that leaves a person feeling cheated afterwards.

What astrology is: a tradition of interpretation, closer to reading a text than to taking a measurement. It works as language — it organises experience into categories that give you something to think with. The worth of a reading is measured by what the person manages to do with it, and that is an honest criterion.

And there are things you can demand of any astrologer without arguing about belief at all. Four of them, and they separate work from idle talk:

• That the calculation be correct. Planet position, degree, house and transit date come from an astronomical table. A wrong number there is no difference of school, it is a mistake.
• That the reading say where it gets what it says. If a claim comes from a tradition, a school or an author, the name fits in the sentence. According to astrologers is not a source.
• That the system be declared. The division into houses changes the chart, and different schools cut it differently. A reading that does not say which system it used is hiding half of its own arithmetic.
• That nothing be promised beyond tendency. Event dates, lucky numbers and guaranteed outcomes are not astrology — they are the part that gets sold when the reading has nothing to say.

Anyone who demands those four can judge an astrologer without understanding astrology, and that is why they are written down here.

What astrology does not answer

It does not diagnose illness and it does not speak of death. No chart configuration is a medical report, and whoever reads the sky has no licence to play with another person's fear about their own body. The same holds for legal decisions, for investment and for treatment: a reading can give context, and it replaces no professional.

It decides for nobody. A chart shows leanings, costs and easy paths — the choice stays with whoever lives the life. A reading that orders somebody to quit a job or end a marriage has stepped out of its place.

And without the time of birth it answers by half. The signs of the planets are calculated from the date; the Ascendant and the twelve houses require time and city. It is honest to know which of the two halves a reading is talking about — and whoever does not know the time has routes available, all of them with the price said out loud.

Frequently asked questions about astrology