The first printed edition of Ptolemy's 'Tetrabiblos', originally circulated as a Greek manuscript, subsequently translated into Arabic, and then into Latin in 1138 by Plato Tiburtinus (i.e. "Plato of Tivoli", fl Barcelona 1116-1138), and here issued by Erhard Ratdolt (1442-1528), a German publisher of Arabic works operating in Venice. He printed the work with the complementary 'Centiloquium' – 'Hundred aphorisms' - attributed, at the time, to Ptolemy, along with "Haly"'s explanatory commentary, as stated in the colophon: 'cum Centiloquio eiusdem Ptholomei: [et] co[m]mento Haly, feliciter finit...'. "Haly" is now widely believed to be Ahmad ibn Yusuf al-Misri (c988-1061), and in fact the author of the 'Centiloquium', not just its explicator. The first printed edition of the Greek text was not published until 1535, by Joachim Camerarius.

Ptolemy's scientific studies of the known universe are divided between his three greatest works: the 'Algamest', of astronomy and the heavens; the 'Geographia', an atlas and gazetteer of the earth; and the 'Tetrabiblos', of astrology, which is the applied branch of astronomy: how the heavenly universe affects events on earth.

Ptolemy based each of these works on mathematical calculations. In the case of the 'Algamest', the positions and the motions of the seven planets - the sun, the moon, Saturn, Jupiter, Mercury, Mars, and Venus – in a geocentric cosmography, are described. Ptolemy's study of the influence that the positions and motions of the planets and stars had over specific geographic places, was the 'Tetrabiblos' – 'Mathematical treatise in four books'. The nature of different regions, the qualities of their terrain, meteorology, the temperaments and even the complexions of their inhabitants, are all linked to the celestial influences that were specific to a particular place, and described by Ptolemy in specific "chorographies", which include a study of regional cartography as well as a textual description of cities and places.

Ptolemy's 'Tetrabiblos' advances a theory of mathematical astrology, which deals with all possible celestial figures, with their primary characteristics being derived from their positions relative to the solstices and the equinoxes. It explores real, present causes of natural elements and events, establishing the field of Astrology as a significant and reliable part of natural philosophy, and not just a muddle of myth, magic and superstition. Physical, astronomical, and climatological effects of the stars, can be used, for example, to predict the weather: the sun rising or setting in a clear and unobscured sky, signifies fair weather; the position of the sun in Cancer, in June and July, usually forecasts fair and warm weather; the sun in Leo, in July and August, is associated with hot and steamy weather.

Ptolemy "is unique in his attempt to establish a scientific foundation for astrology: he states the basic concepts of his system of astrology, then works out the details of that system, trying to unify the diverse phenomena of the cosmos under the given set of concepts. He consistently applies this scientific program in determining the physical nature of the stars and signs and their effects on the environment, laying down in advance the relatively few concepts which fix their individual characteristics, then showing how these characteristics can be used to forecast the weather, human nature in various climes, and some eclipse effects" (Riley).

However, more complex calculations are offered too: Ptolemy has "axioms" of stellar geometry on which to base a scientific astrology. "The axioms specify two sets of significant points on the ecliptic. One set of points depends on the position of the ecliptic relative to the horizon. These points, the centers or angles, are the Ascendant, the point on the eastern horizon; Midheaven (MC), the point of the ecliptic on the noon meridian; the Descendant, the point on the western horizon; and Lower Midheaven (IC), the point opposite MC, directly below the earth. The other set of significant points is defined relative to the motion of the sun on the ecliptic. These are the two tropics or solstices, the points at which the sun has come farthest north or south and begins to turn, and the two equinoxes, where the sun crosses the equator... The second set of geometrical axioms defines the nature of the signs' and stars' inter-relationships, and are all based on degree intervals evenly divisible into 360: 60 (sextile), 90 (square), 120 (trine), and 180 (op- position)" (Riley).

To illustrate his theory, Ptolemy provides two schematic quadrant maps of the inhabited world. The first divides the world into four quarters: the section to the extreme south of the Tropic of Cancer, is hot and dry, and is inhabited by fiery people; in the extreme northern part, "under the Bears", it is cold and moist, and the inhabitants are equally temperamental; then there is a temperate zone, between the Tropic of Cancer and "the Bears", divided into an east and west, inhabited by moderately tempered people. In his second map, Ptolemy establishes a cultural unity around the Mediterranean basin: "the east-west line runs through the Straits of Gibraltar to the Gulf of Issus, the north-south line through the Black Sea and the Gulf of Suez and the Red Sea. Each quadrant is under the control of one of the stellar triangles. The NW triangle controls the NW quadrant, and so on. Control by a particular triangle also implies control by the stars which rule the triangle; hence Jupiter and Mars rule both the NW triangle and the NW quadrant" (Riley).

The influence of Ptolemy's 'Tetrabiblos' extended for more than fifteen hundred years before it was superseded in its authority by Copernicus's heliocentric theory of the universe. Well into the sixteenth century, authors aimed to describe New World lands following Ptolemy's principles as expressed in his 'Geographia' and the 'Tetrabiblos'.

Rare: only two institutional examples are known, at the Smithsonian, and in the national library of Sweden; only one other example is known in commerce.