Gemini

Gemini is the third sign of the zodiac and the first of the air signs. This year the Sun is in Gemini from 21 May to 21 June 2026. The old books call it a double sign: Ptolemy’s word is “bicorporeal”, William Lilly’s is “double-bodied”, and our data uses the modern word, mutable.

A sign between two others

Ptolemy defines Gemini’s kind of sign by its neighbours. “The bicorporeal signs severally follow the fixed signs; and, being thus intermediately placed between the fixed and the tropical signs, they participate in the constitutional properties of both, from their first to their last degrees.”

For Gemini the neighbours are Taurus, a fixed sign, and Cancer, the sign in which Ptolemy has the Sun turn and bring summer to the northern hemisphere. Our reading of that is that Gemini has no season of its own to open or to settle. It shares in the one before it and the one after it.

He also counts it masculine. His third triplicity “is composed of Gemini, Libra, and Aquarius, masculine signs”.

Mercury’s house

Ptolemy’s reason for giving Gemini to Mercury is the planet’s place in the sky: “Mercury never has greater distance from the Sun than the space of one sign, and is beneath all the other planets: hence he is placed nearest to both luminaries, and the remaining two signs, Gemini and Virgo, are allotted to him.” The luminaries are the Sun and the Moon, whose houses are Leo and Cancer, and Gemini is the sign beside Cancer.

Mercury appears again in the triplicity. Ptolemy writes that it “holds connection with Saturn and Mercury by containing their houses”, and that “Saturn rules it by day” and “Mercury by night”.

His chapter on exaltations gives every planet a sign of exaltation and a sign of fall, and Gemini is neither for any of them. Ptolemy places no exaltation or fall in Gemini; what he gives it is Mercury, by house and, by night, in the triplicity.

The Gemini character, as the old books give it

Lilly’s line calls Gemini “an aerial, hot, moyst, sanguine, Diurnal, common or double-bodied humane Signe” and “the diurnall house of” Mercury. “Common” is his word for mutable, and “humane” names the human signs. He is listing qualities for judging a chart, not describing people.

Alan Leo describes people, and doubleness runs through what he says. “These persons are rarely content with a single occupation or pursuit, and seem to delight in having two things in hand at the same time.” He piles up opposites: “They can present a bold front and assertive attitude, and yet be timid and highly nervous.” And: “They are conservative and progressive, and altogether quite dualistic subjects, which makes them difficult for others to understand.”

He does not treat the trait only as a fault. Of Gemini people he writes that “they must have diversity; this may make them appear to their friends very fickle and indecisive, but it is their particular way of working, therefore perfectly legitimate to them”. His warning comes with a condition: “when they live the unbalanced personal life, they become very diffusive, indecisive and unreliable”.

Setting Alan Leo’s “dualistic subjects” beside the double-bodied sign of Ptolemy and Lilly is our comparison. The passages we quote do not make that link themselves.

An air sign among three

Libra and Aquarius are the other two air signs. In the list of matches below, which comes from our formula, those two come first, Gemini with Gemini is next, and the fire signs Aries and Leo follow. Sagittarius, the sign opposite Gemini, comes after them, and Capricorn is last. The method is on how we score.

Set beside that list, which is our comparison, Alan Leo’s single sentence on marriage for this sign reads: “These persons would do well to marry those born in the airy or fiery triplicities.” That is a nineteenth-century astrologer’s view of signs, quoted as history, and not advice about a relationship.