The Stoics

Aristotle's science became the standard in ancient Rome. The Stoic philosophers of that period were the first to develop a mathematical astrology based on these notions. The Stoics taught a doctrine of "cosmic sympathy" - that everything in the world was interconnected and influenced everything else, beginning with the influence of the stars. The Stoics believed in an unalterable fate - that emanations from the stars resulted in an inevitable human destiny, with no free will to alter the outcome of any events.
To support this view, the ancients noted the physical influence of the Sun and Moon in the natural world. They noted, as we do, that variations in sunlight and heat caused the changes in the seasons. They saw that the Moon raised the tide and that certain plants - heliotropes such as sunflowers - would turn to face the Sun as it crossed the sky. From that, they imagined that the celestial bodies exerted other influences over the world, including human affairs. The Stoics and their successors devised an elaborate scheme for assigning arbitrary meanings to the Sun, Moon, planets, and also the constellations of the zodiac, based upon flawed premises of Greek pseudoscience.
As astrology assumed its current form, contrary qualities were assigned to the celestial bodies. For obvious reasons, the Sun was regarded as being hot and dry. The Moon, being it's opposite, was regarded as cold and moist. It was believed that the Moon caused rain and dew to form on the Earth. These phenomena are explained today by the modern science of meteorology and are found to have nothing to do with the Moon. Other properties were arbitrarily assigned to the visible planets and also the zodiac constellations. For example, astrology associates the four elements with the constellations, so that there are "earth signs," "water signs," etc. Of course there are no such properties to the constellations except what was dreamed up in the minds of pagan astrologers centuries ago. 
In Greek astrological pseudoscience, many bizarre associations were made between the Sun, Moon, and planets and tangible objects on Earth. For example, certain plants came to be associated with each planet, as were certain gemstones. This pagan tradition survives today as "birthstones" that people wear in rings and necklaces. There were seven metals known in the ancient world, and these were associated with the seven classical planets. For obvious reasons, gold and silver were respectively connected with the Sun and Moon. Copper was associated with Venus, since the earliest copper mines were found on the island of Cyprus, whose ancient people worshipped this false goddess. (This name is pronounced "kupros" in Greek, which is the Greek word for copper.) Mars was associated with iron, Mercury with quicksilver, and Jupiter with tin.
The notion of contrary qualities was a part of the ancient medicine of the Greek physician Galen, who taught that our bodies had four "tempers" or "humors" corresponding to the four elements - blood, phlegm, bile and melancholy. All disease was believed to be caused by an imbalance or "distemper" in these fluids. The practice of "bleeding" patients to cure disease was performed in an attempt to restore a proper healthy balance. Also, in Galen's medicine, it was believed that each part of the body was "ruled" by a zodiac constellation, and that certain medical procedures could only be performed at certain times, based on favorable positions of the constellations. In spite of all the medical pseudoscience, our ancestors somehow survived!
The idea of cosmic sympathy and the interconnectedness of all things led to all manner of bizarre divination and superstition. Omens were found everywhere and in everything. The superstitious idea of "reading" palms or tea leaves comes from this idea, since it was believed that such interconnectedness would show up in random arrangements of commonplace things. In Rome, animals were sacrificed and their livers were studied in the belief that the shapes of the organs indicated cosmic sympathy and could thus read the future. Even the paths of birds in flight were studied to discover new omens. A stumble or a stubbed toe was taken as a bad omen. And of course, the ancient superstition of lucky and unlucky days still persists today as "Friday the 13th." The Romans were addicted to these superstitions. The Gospel of Christ first took root in this culture. No doubt the transforming power of Jesus released many Romans from the fatalistic tyranny of astrology and divination.

*This article published November 7, 2007.

This article is from the Classical Astronomy Update, a free email newsletter for Christian homeschoolers. Jay Ryan is also the author of "Signs & Seasons," an astronomy homeschool curriculum. For more information, visit his web site