In the pre-modern period, astrology has been the practice of relating celestial bodies to lives and events on earth and the resulting tradition. One aspect of astrology was based on the knowledge of astronomy and mathematical calculations, and the other aspect dealt with soothsaying. We can talk about two types of astrology: natural astrology and judicial astrology. Natural astrology has admitted the idea of celestial influences of a general nature, such as would affect the weather or the environment of a patient, and thus his chances of healing. Judicial astrology aims to determine the particular effects of the stellar influences on a specific person, with a view toward forecasting the future.
 But it is noteworthy that many sciences in the pre-modern period used astronomical results. Thus, understanding the knowledge related to climate, agriculture and medicine in the pre-modern era is not complete without understanding astrology. In this article, in the first part, we try to briefly describe astrology and its types and enumerate some features of medical astrology as part of natural astrology. In the second part, we will examine how astrology influenced the medical theories of Hippocrates and Galen in ancient Greece. And we show that medical astrology for them has been part of the natural process of explaining diseases and methods of prognosis and treatment and prevention.
 Our method in this article is the hermeneutic-based author understanding method. In other words, in this article, we do not use modern ideas about astrology, but try to examine medical astrology based on the natural and judicial astrology, which were expressed in the same pre-modern era. Thus, we show that astrology was not only an important science in its time, but was also related to the various sciences of its time, so that the understanding of knowledge related to medicine in the pre-modern would be incomplete without understanding astronomy.
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