Possibly the oldest form of divination known, astrology assumes the physical world to be a reflection of the cosmos, "As above, So below." Astrology uses the relative positions and movements of the Sun, Moon, planets, and lunar nodes to understand human lives and reality in the world.

Throughout history there have been many systems of interpretation, including the Chaldean, Babylonian, Chinese, Hindus, Tibetan, Mayan, and, of course, the Greek.

The Greek system is the one in use today in the West. It is largely based upon Ptolemy's book, known as the Tetrabiblios, or the "Four Books on the Influence of the Stars." It was the Greeks that first made astrology accessible to the general public.