This is part 1 of 2. Part 2 is here.
Τὴν δὲ τοῦ Ῥομπέρτου τελευτὴν μαθηματικός τις Σὴθ καλούμενος μεγάλα ἐπ’ ἀστρολογίᾳ αὐχῶν, μετὰ τὴν εἰς τὸ Ἰλλυρικὸν αὐτοῦ διαπεραίωσιν προειρήκει διὰ χρησμοῦ, ὃν ἐν χάρτῃ ἐκθέμενος καὶ σφραγίσας, τισὶ τῶν τοῦ βασιλέως οἰκειοτάτων ἐνεχείρισε, παραγγείλας κατέχειν αὐτὸν μέχρι τινός. εἶτα τοῦ Ῥομπέρτου τετελευτηκότος, ἐξ ἐπιταγῆς αὐτοῦ λύουσι τὸν χάρτην. εἶχε δὲ ὁ χρησμὸς οὕτως· “μέγας ἐχθρὸς ἐξ ἑσπέρας πολλὰ κυκήσας ἄφνω πεσεῖται.” ἐθαύμασαν μὲν οὖν πάντες τὴν τοῦ ἀνδρὸς ἐπιστήμην· ἦν γὰρ ἐπὶ ταύτῃ τῇ σοφίᾳ εἰς ἄκρον ἐληλακώς. καὶ ἵνα τι βραχὺ παραδράμωμεν, τοῦ λόγου τῆς ἱστορίας μικρὸν ἀποστάντες, οὕτως ἔχει τὰ κατὰ τοὺς χρησμούς. νεώτερον μὲν τὸ ἐφεύρεμα, καὶ οὐκ οἶδε ταύτην τὴν ἐπιστήμην ὁ πάλαι χρόνος. οὔτε γὰρ ἐπ’ Εὐδόξου τοῦ ἀστρονομικωτάτου ἡ τῶν χρησμῶν μέθοδος ἦν, οὔτε ὁ Πλάτων τὴν σύνεσιν ταύτην ᾔδει, ἀλλ’ οὐδὲ Μανέθων ὁ ἀποτελεσματικὸς περὶ ταύτης ἠκρίβωκεν. ἀλλὰ λῆψις ἦν ἐκείνοις ὡροσκόπου, ἐν οἷς προὐμαντεύοντο, καὶ πῆξις τῶν κέντρων καὶ τοῦ ὅλου διαθέματος ἐπιτήρησις καὶ ὁπόσα ἄλλα ὁ τὴν μέθοδον ταύτην εὑρηκὼς τοῖς ἐς ὕστερον παρέδωκεν, ἅπερ ξυνετὰ τοῖς περὶ τὰ τοιαῦτα ματαιάζουσιν. ἡμεῖς δὲ ἐκεῖθέν ποτε ὀλίγον τι τῆς ἐπιστήμης ταύτης ἡψάμεθα, οὐχ ἵνα τι τοιοῦτον διαπραξαίμεθα (μὴ γένοιτο), ἀλλ’ ἵνα τῆς ματαιολογίας ταύτης ἀκριβέστερον καταγνόντες, καὶ τῶν περὶ αὐτὴν ἠσχολημένων καταγινώσκοιμεν. ταῦτα δὲ γράφω οὐκ ἐπιδείξεως ἕνεκα, ἀλλ’ ἵνα ἐνδειξαίμην ὅτι ἐπὶ τοῦ αὐτοκράτορος τούτου πολλαὶ τῶν ἐπιστημῶν εἰς ἐπίδοσιν ἐληλύθεισαν, τιμῶντος τοὺς φιλοσόφους καὶ φιλοσοφίαν αὐτήν, εἰ καὶ πρὸς τὸ μάθημα τοῦτο τῆς ἀστρολογίας δυσχεραίνων πως κατεφαίνετο, οἶμαι, διότι τοὺς πολλοὺς τῶν ἀκεραιοτέρων ἀφίστασθαι ἀνέπειθε τῶν ἄνωθεν ἐλπίδων καὶ κεχηνέναι τοῖς ἀστράσιν. αὕτη αἰτία γέγονε πόλεμον ἔχειν τὸν αὐτοκράτορα πρὸς τὸ μάθημα τῆς ἀστρολογίας.
(Anna Comnena, Alex. 6.7.4-5)
A certain mathematician named Seth who boasted much of his knowledge of astrology had forecast Robert’s fate by an oracle, after his crossing to Illyria, written this forecast on a paper, sealed it and entrusted it to some of the Duke’s intimates, bidding them keep it till a certain time. After Robert’s death they opened it by the astrologer’s order and the prophecy was as follows: “A great enemy from the west shall fall suddenly after having stirred up great confusion.” This caused everybody to marvel at the man’s knowledge; and in truth he had delved very deeply into this branch of science, and if I may be allowed to make a short break in the course of my history, the following are the facts about astrological prophecies. The discovery is fairly recent, and the science of it was not known to the ancients. For this method of divination did not exist in the time of Eudoxus, the greatest of all astronomers, neither did Plato have any knowledge of it, and even the astrologer, Manetho, had not brought it to perfection. Now these (astrologers) observe the hour of the birth of the persons about whom they intend to prophesy, and fix the cardinal points and carefully note the disposition of all the stars, in short they do everything that the inventor of this science bequeathed to posterity and which those who trouble about such trifles understand. We, also, at one time dabbled a little in this science, not in order to cast horoscopes (God forbid!), but by gaining a more accurate idea of this vain study to be able to pass judgment upon its devotees. I do not mention this for the sake of boasting, but to prove that during my father’s reign many of the sciences made great progress, as he honoured both philosophers and philosophy itself, but towards this teaching of astrology he showed some hostility, I believe because it tended to make people of a guileless nature reject their faith in God and gape at the stars. This was the cause of the Emperor’s waging war against the teaching of astrology. (tr. Elizabeth Dawes)