Of Ptolemy’s genuine works the most germane to and significant for our investigation is his _Tetrabiblos_, _Quadripartitum_, or four books on the control of human life by the stars. It seems to have been translated into Latin by Plato of Tivoli in the first half of the twelfth century[509] before _Almagest_ or _Geography_ appeared in Latin. In the middle of the thirteenth century Egidius de Tebaldis, a Lombard of the city of Parma, further translated the commentary of Haly Heben Rodan upon the _Quadripartitum_.[510] In the early Latin editions[511] the text is that of the medieval translation; in the few editions giving a Greek text there is a different Latin version translated directly from this Greek text.[512] [Sidenote: A genuine reflection of Ptolemy’s approval of astrology.] In the _Tetrabiblos_ the art of astrology receives sanction and exposition from perhaps the ablest mathematician and closest scientific observer of the day or at least from one who seemed so to succeeding generations. Hence from that time on astrology was able to take shelter from any criticism under the aegis of his authority. Not that it lacked other exponents and defenders of great name and ability. Naturally the authenticity of the _Tetrabiblos_ has been questioned by modern admirers of Hellenic philosophy and science who would keep the reputations of the great men of the past free from all smudge of superstition. But Franz Boll has shown that it is by Ptolemy by a close comparison of it with his other works.[513] The astrological _Centiloquium_ or _Karpos_, and other treatises on divination and astrological images ascribed to Ptolemy in medieval Latin manuscripts are probably spurious, but there is no doubt of his belief in astrology. German research as usual regards its favorite Posidonius as the ultimate source of much of the _Tetrabiblos_, but this is not a matter of much consequence for our present investigation. [Sidenote: Validity of astrology.]