If we consider the reasoning now commonly thought valid in favour of the doctrine that other orbs besides our earth are inhabited, and compare it with the reasoning on which judicial astrology was based, we shall not find much to choose between the two, so far as logical weight is concerned. Because the only member of the solar system which we can examine closely is inhabited, astronomers infer a certain degree of probability for the belief that the other planets of the system are also inhabited. And because the only sun we know much about is the centre of a system of planets, astronomers infer that probably the stars, those other suns which people space, are also the centres of systems; although no telescope which man can make would show the members of a system like ours, attending on even the nearest of all the stars. The astrologer had a similar argument for his belief. The moon, as she circles around the earth, exerts a manifest influence upon terrestrial matter—the tidal wave rising and sinking synchronously with the movements of the moon, and other consequences depending directly or indirectly upon her revolution around the earth. The sun's influence is still more manifest; and, though it may have required the genius of a Herschel or of a Stephenson to perceive that almost every form of terrestrial energy is derived from the sun, yet it must have been manifest from the very earliest times that the greater light which rules the day rules the seasons also, and, in ruling them, provides the annual supplies of vegetable food, on which the very existence of men and animals depends. If these two bodies, the sun and moon, are thus potent, must it not be supposed, reasoned the astronomers of old, that the other celestial bodies exert corresponding influences? We know, but they did not know, that the moon rules the tides effectually because she is near to us, and that the sun is second only to the moon in tidal influence because of his enormous mass and attractive energy. We know also that his position as fire, light, and life of the earth and its inhabitants, is due directly to the tremendous heat with which the whole of his mighty frame is instinct. Not knowing this, the astronomers of old times had no sufficient reason for distinguishing the sun and moon from the other celestial bodies, so far at least as the general question of celestial influences was concerned.
So far as particulars were concerned, it was not altogether so clear to them as it is to us, that the influence of the sun must be paramount in all respects save tidal action, and that of the moon second only to the sun's in other respects, and superior to his in tidal sway alone. Many writers on the subject of life in other worlds are prepared to show (as Brewster attempts to do, for example) that Jupiter and Saturn are far nobler worlds than the earth, because superior in this or that circumstance. So the ancient astronomers, in their ignorance of the actual conditions on which celestial influences depend, found abundant reasons for regarding the feeble influences exerted by Saturn, Jupiter, and Mars, as really more potent than those exerted by the sun himself upon the earth. They reasoned, as Milton afterwards made Raphaël reason, that 'great or bright infers not excellence,' that Saturn or Jupiter, though 'in comparison so small, nor glist'ring' to like degree, may yet 'of solid good contain more plenty than the sun.' Supposing the influence of a celestial body to depend on the magnitude of its sphere, in the sense of the old astronomy (according to which each planet had its proper sphere, around the earth as centre), then the influence of the sun would be judged to be inferior to that of either Saturn, Jupiter, or Mars; while the influences of Venus and Mercury, though inferior to the influence of the sun, would still be held superior to that of the moon. For the ancients measured the spheres of the seven planets of their system by the periods of the apparent revolution of those bodies around the celestial dome, and so set the sphere of the moon innermost, enclosed by the sphere of Mercury, around which in turn was the sphere of Venus, next the sun's, then, in order, those of Mars, Jupiter, and Saturn. We can readily understand how they might come to regard the slow motions of the sphere of Saturn and Jupiter, taking respectively some thirty and twelve years to complete a revolution, as indicating power superior to the sun's, whose sphere seemed to revolve once in a single year. Many other considerations might have been urged, before the Copernican theory was established, to show that, possibly, some of the planets exert influences more effective than those of the sun and moon.
It is, indeed, clear that the first real shock sustained by astrology came from the arguments of Copernicus. So long as the earth was regarded as the centre round which all the celestial bodies move, it was hopeless to attempt to shake men's faith in the influences of the stars. So far as I know, there is not a single instance of a believer in the old Ptolemaic system who rejected astrology absolutely. The views of Bacon—the last of any note who opposed the system of Copernicus4—indicate the extreme limits to which a Ptolemaist could go in opposition to astrology. It may be worth while to quote Bacon's opinion in this place, because it indicates at once very accurately the position held by believers in astrology in his day, and the influence which the belief in a central fixed earth could not fail to exert on the minds of even the most philosophical reasoners.
'Astrology,' he begins, 'is so full of superstition that scarce anything sound can be discovered in it; though we judge it should rather be purged than absolutely rejected. Yet if any one shall pretend that this science is founded not in reason and physical contemplations, but in the direct experience and observation of past ages, and therefore not to be examined by physical reasons, as the Chaldæans boasted, he may at the same time bring back divination, auguries, soothsaying, and give in to all kinds of fables; for these also were said to descend from long experience. But we receive astrology as a part of physics, without attributing more to it than reason and the evidence of things allow, and strip it of its superstition and conceits. Thus we banish that empty notion about the horary reign of the planets, as if each resumed the throne thrice in twenty-four hours, so as to leave three hours supernumerary; and yet this fiction produced the division of the week,5 a thing so ancient and so universally received. Thus likewise we reject as an idle figment the doctrine of horoscopes, and the distribution of the houses, though these are the darling inventions of astrology, which have kept revel, as it were, in the heavens. And lastly, for the calculation of nativities, fortunes, good or bad hours of business, and the like fatalities, they are mere levities, that have little in them of certainty and solidity, and may be plainly confuted by physical reasons. But here we judge it proper to lay down some rules for the examination of astrological matters, in order to retain what is useful therein, and reject what is insignificant. Thus, 1. Let the greater revolutions be retained, but the lesser, of horoscopes and houses, be rejected—the former being like ordnance which shoot to a great distance, whilst the other are but like small bows, that do no execution. 2. The celestial operations affect not all kinds of bodies, but only the more sensible, as humours, air, and spirits. 3. All the celestial operations rather extend to masses of things than to individuals,