Libra is the seventh sign, beginning at the autumnal equinox, the second of the two moments when day and night are equal, and it is cardinal, airy and ruled by Venus, with Saturn taking its exaltation there. It stands opposite Aries, and the classical scheme reads the whole second half of the zodiac as turned outward toward other people where the first half is turned inward toward the self, so Libra begins the signs of relationship, contract and the other party. The Venusian rulership works here through air rather than earth, giving the social and aesthetic side of the planet: agreement, proportion, courtesy, and the judgment of what is fitting. Saturn's exaltation adds the sterner note of law, weight and consequence that the scales imply, and the classical sources on legal questions make regular use of it.
Libra's three decans run Moon, Saturn, Jupiter, continuing the unbroken sequence from Virgo's final Mercury decan. As an air sign, Libra's triplicity is Saturn by day and Mercury by night in both the Ptolemaic and Dorothean tables, agreeing exactly with Gemini and Aquarius, the sign's fellow air signs; the disagreement between the classical authorities is confined to the water triplicity alone. Manilius, writing under Augustus, connects Libra's balance directly to Roman ideas of civic justice and even suggests a flattering link between the sign and the emperor's own even-handed rule, an early instance of imperial flattery folded into supposedly neutral astrological doctrine.