A very few considerations would make it apparent to all that a certain power emanating from the eternal ethereal substance is dispersed through and permeates the whole region about the earth, which throughout is subject to change, since, of the primary sublunary elements, fire and air are encompassed and changed by the motions in the ether, and in turn encompass and change all else, earth and water and the plants and animals therein. For the sun, together with the ambient, is always in same way affecting everything on the earth, not only by the changes that accompany the seasons of the year to bring about the generation of animals, the productiveness of plants, the flowing of waters, and the changes of bodies, but also by its daily revolutions furnishing heat, moisture, dryness, and cold in regular order and in correspondence with its positions relative to the zenith. The moon, too, as the heavenly body nearest the earth, bestows her effluence most abundantly upon mundane things, for most of them, animate or inanimate, are sympathetic to her and change in company with her; the rivers increase and diminish their streams with her light, the seas turn their own tides with her rising and setting, and plants and animals in whole or in same part wax and wane with her. Moreover, the passages of the fixed stars and the planets through the sky often signify hot, windy, and snowy conditions of the air, and mundane things are affected accordingly. Then, too, their aspects to one another, by the meeting and mingling of their dispensations, bring about many complicated changes. For though the sun’s power prevails in the general ordering of quality, the other heavenly bodies aid or oppose it in particular details, the moon more obviously and continuously, as for example when it is new, at quarter, or full, and the stars at greater intervals and more obscurely, as in their appearances, occultations, and approaches. If these matters be so regarded, all would judge it to follow that not only must things already compounded be affected in same way by the motion of these heavenly bodies, but likewise the germination and fruition of the seed must be moulded and conformed to the quality proper to the heavens at the time. The more observant farmers and herdsmen, indeed, conjecture, from the winds prevailing at the time of impregnation and of the sowing of the seed, the quality of what will result; and in general we see that the more important consequences signified by the more obvious configurations of sun, moon, and stars are usually known beforehand, even by those who inquire, not by scientific means, but only by observation. Those which are consequent upon greater forces and simpler natural orders, such as the annual variations of the seasons and the winds, are comprehended by very ignorant men, nay even by some dumb animals; for the sun is in general responsible for these phenomena. Things that are not of so general a nature, however, are comprehended by those who have by necessity become used to making observations, as, for instance, sailors know the special signs of storms and winds that arise periodically by reason of the aspects of the moon and fixed stars to the sun. Yet because they cannot in their ignorance accurately know the times and places of these phenomena, nor the periodic movements of the planets, which contribute importantly to the effect, it happens that they often err. If, then, a man knows accurately the movements of all the stars, the sun, and the moon, so that neither the place nor the time of any of their configurations escapes his notice, and if he has distinguished in general their natures as the result of previous continued study, even though he may discern, not their essential, but only their potentially effective qualities, such as the sun’s heating and the moon’s moistening, and so on with the rest; and if he is capable of determining in view of all these data, both scientifically and by successful conjecture, the distinctive mark of quality resulting from the combination of all the factors, what is to prevent him from being able to tell on each given occasion the characteristics of the air from the relations of the phenomena at the time, for instance, that it will be warmer or wetter? Why can he not, too, with respect to an individual man, perceive the general quality of his temperament from the ambient at the time of his birth, as for instance that he is such and such in body and such and such in soul, and predict occasional events, by use of the fact that such and such an ambient is attuned to such and such a temperament and is favourable to prosperity, while another is not so attuned and conduces to injury? Enough, however; for the possibility of such knowledge can be understood from these and similar arguments.
The following considerations might lead us to observe that criticism of the science on the score of impossibility has been specious but undeserved. In the first place, the mistakes of those who are not accurately instructed in its practice, and they are many, as One would expect in an important and many-sided art, have brought about the belief that even its true predictions depend upon chance, which is incorrect. For a thing like this is an impotence, not of the science, but of those who practise it. Secondly; most, for the sake of gain, claim credence for another art in the name of this, and deceive the vulgar, because they are reputed to foretell many things, even those that cannot naturally be known beforehand, while to the more thoughtful they have thereby given occasion to pass equally unfavourable judgement upon the natural subjects of prophecy. Nor is ibis deservedly done; it is the same with philosophy-we need not abolish it because there are evident rascals among those that pretend to it. Nevertheless it is clear that even though One approach astrology in the most inquiring and legitimate spirit possible, he may frequently err, not for any of the reasons state, but because of the very nature of the thing and his own weakness in comparison with the magnitude of his profession. For in general, besides the fact that every science that deals with the quality of its subject-matter is conjectural and not to be absolutely affirmed, particularly One which is composed of many unlike elements, it is furthermore true that the ancient configurations of the planets, upon the basis of which we attach to similar aspects of our own day the effects observed by the ancients in theirs, Can be more Or less similar to the modern aspects, and that, too, at long intervals, but not identical, since the exact return of all the heavenly bodies and the earth to the same positions, unless One holds vain opinions of his ability to comprehend and know the incomprehensible, either takes place not at all or at least not in the period of time that falls within the experience of man; so that for this reason predictions sometimes fail, because of the disparity of the examples on which they are based. As to the investigation of atmospheric phenomena, this would be the only difficulty, since no other cause besides the movement of the heavenly bodies is taken into consideration. But in an inquiry concerning nativities and individual temperaments in general, One can see that there are circumstances of no small importance and of no trifling character, which join to cause the special qualities of those who are born. For differences of seed exert a very great influence on the special traits of the genus, since, if the ambient and the horizon are the same, each seed prevails to express in general its own form, for example, man, horse, and so forth; and the places of birth bring about no small variation in what is produced. For if the seed is generically the same, human for example, and the condition of the ambient the same, those who are born differ much, both in body and soul, with the difference of countries. In addition to this, all the aforesaid conditions being equal, rearing and customs contribute to influence the particular way in which a life is lived. Unless each One of these things is examined together with the causes that are derived from the ambient, although this latter be conceded to exercise the greatest influence (for the ambient is One of the causes for these things being what they are, while they in turn have no influence upon it), they can cause much difficulty for those who believe that in such cases everything can be understood, even things not wholly within its jurisdiction, from the motion of the heavenly bodies alone.
Since this is the case, it would not be fitting to dismiss all prognostication of this character because it can sometimes be mistaken, for we do not discredit the art of the pilot for its many errors; but as when the claims are great, so also when they are divine, we should welcome what is possible and think it enough. Nor, further, should we gropingly and in human fashion demand everything of the art, but rather join in the appreciation of its beauty, even in instances wherein it could not provide the full answer; and as we do not find fault with the physicians, when they examine a person, for speaking both about the sickness itself and about the patient’s idiosyncrasy, so too in this case we should not object to astrologers using as a basis for calculation nationality, country, and rearing, or any other already existing accidental qualities.