CLAUDIUS PTOLEMY:

TETRABIBLOS

OR THE QUADRIPARTITE MATHEMATICAL TREATISE

4. Method of Making Particular Predictions.

After this introductory exanimation it would be the next task to deal briefly with the procedure of the predictions, and first with those concerned with general conditions of countries or cities. The method of the inquiry will be as follows: The first and most potent cause of such events lies in the conjunctions of the sun and moon at eclipse and the movements of the stars at the time. Of the prediction itself, one portion is regional; therein we must foresee for what countries or cities there is significance in the various eclipses or in the occasional regular stations of the planet, that is, of Saturn, Jupiter, and Mars, whenever they halt, for then they are significant. Another division of the prediction is chronological; therein the need will be to foretell the time of the portents and their duration. A part, too, is generic; through this we ought to understand with what classes the event will be concerned. And finally there is the specific aspect, by which we shall discern the quality of the event itself.



Ptomely's Tetrabiblos

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