Fixed

Taurus, Leo, Scorpio and Aquarius are the signs the Sun occupies in the middle month of each season. Ptolemy calls them the solid signs, stereos, and the reason he gives is meteorological: while the Sun passes through them, the character of the season is settled and fully itself rather than arriving or departing.

That is the whole of the doctrine and everything else follows from it. The tradition reads the fixed signs for holding a position, resisting change and seeing a thing through, and for the difficulty of moving anything that has settled into them. Their reputation for stubbornness is a fair reading of the same property from the other side.

The group has an unusual afterlife outside astrology. The four are represented by a bull, a lion, an eagle and a man, and that set of figures appears in the vision of Ezekiel, in the four living creatures of the book of Revelation, in the four evangelists of Christian iconography, and on the World and the Wheel of Fortune in the tarot. Whether the correspondence runs from astrology into the religious imagery, in the other direction, or from a shared older source, is a question with real scholarship on more than one side, and this entry does not settle it.

The eagle for Scorpio is itself a substitution. The sign's own creature is the scorpion, and the eagle appears as its higher form within a tradition of interpretation rather than in the sign's basic definition.

The fixed group is distributed one to each element, like the other two. Taurus is earth, Leo fire, Scorpio water and Aquarius air, and the polarity alternates as it does everywhere else in the zodiac, so Taurus and Scorpio carry the receptive charge and Leo and Aquarius the active one.

What that distribution means in practice is that fixity is not a single flavour. Fixed earth holds a possession, fixed fire holds a position, fixed water holds a feeling and fixed air holds an opinion, and the four are not interchangeable in a reading. The tradition's descriptions of the individual signs carry that distinction and the modal summary does not, which is a general reason to treat the three qualities as one axis of a sign's definition rather than as its character.

The four also stand opposite one another in two pairs, Taurus against Scorpio and Leo against Aquarius, and every sign of a given quality is either opposite or square to every other sign of that quality. That geometry is why the qualities matter structurally: a chart with several planets in fixed signs will usually have them in hard aspect to one another, so the mode is a shorthand for a pattern of tension as well as a description of temperament.

Modern astrology adds the fixed grand cross and reads it for stalemate and endurance, which is a twentieth century elaboration of the same geometry rather than a doctrine drawn from the older sources.