This work describes the main basic concepts of the astrological work of Ptolemy, through an analysis of his Tetrabiblos. Comparing his ideas to those of other authors of his time, it is shown that Ptolemy does not present stoic influences, as claimed by some historians. The conclusion of the article is that the basis of Ptolemy's astrology was Aristotle's physics.

This analysis of Ptolemy's Teatriblos deals with how the social and cultural role of astrology changed between lì and III century a D.: from a practice hard fought, although successful, to a generally accepted branch of knowledge. In Ptolemy's treatise astrology is shown to be not a science but an art: a techne" fallible but not controvertible. As the basis for such a project of reforming common opinion about astrol¬ogy, we find a quiet yielding attitude toward sceptical antidogmatism, and a (...) non-deterministic way of conceiving man 's naturai relationship with heavenly bodies. (shrink)

SUMMARY. The works of Alexander of Aphrodisias were written a few decades after the publication of the most successful -astrology hand- book in antiquity, Ptolemy's Tetrabiblos Syntaxis, which attempts to naturalize astrology, i.e. to make it agree with Aristotelian theory of science. A comparison of the doctrines between the Tetrabiblos and some passages of Alexander'p works on fate demostrates a noteworthy con¬vergere of the two scholars, and probably a dependence of the lasi great greek Aristotle's exegete on the (...) theories of Ptolemaic astrology, at least in reference to three points: theory of fate; justification of de- vining as a technical and naturai conjecture about man's fate; ana¬lysis of the stars' influence on the sublunary world in physical and phi¬losophical terms. (shrink)