Astrology interested itself chiefly with the relative positions of planers and with their conjunctions. Diodorus of Sicily, after recording the Chaldeans assert that planets change their velocities and periods of time, says: These stars exert the greatest influence for both good and evil upon the nativity of men; and it is chiefly from the nature of these planets and the study of them that they know what is in store for mankind.(1)
It is perfectly correct to say as Diodorus did because of the great changes which were brought upon mankind and the nature of everything living on this planet by encounters with other planets. But from the truth of this belief of the Chaldeans and to the wrong conclusions was but a short distance. If the planets at their different encounters caused flood, hurricane, or conflagration, destruction of animals, or appearance of new plants, man could easily conclude that this or that consequence is the result of a special character of this or that planet.
The Chaldeans tried to build their astrology empirically: they noticed every year the movements of the stars, the conjunctions that took place and the political and natural changes in the realm. Very many such observations were made and written down.(2) From the idea that the position of planets influences the nature and the life of nations and kings, to the idea that it influences a single individual, was but one step. A fiery character of some men could be compared with the fiery character of Venus or Mars. In the Tractate Sanhedrin of the Babylonian Talmud it is said that He who is born under Venus will be wealthy and unchaste. What is the reason? Because fire was created therein. . . He who is born under Mars will be a shedder of blood.(3)
It was supposed that the position of planets in the hour of conception is fateful for the building of the character and also for the future of the individual. So for example in the book of Hindi; astrology. The Bri-hajgatakam of Varaha Mihira, it is said: When Venus and Saturn are in one sign, persons become short-sighted, earn money, and increase it through their wives or young women, are authors and painters . . .(4) Sahagun reports that among the Aztecs soothsayers who tell the good or bad fortune children are going to have, according to the date, time or signs of their birth.(5)