18. There is a well-known theorem which proves that the Zodiac, like the planets, moves from west to east at the rate of one part in a hundred years, and that this movement in the lapse of so long a time changes the local relation of the signs; so that, on the one hand, there is the invisible sign, and on the other, as it were, the visible figure of it; and events, they say, are discovered not from the figure, but from the invisible sign; though it cannot possibly be apprehended. But let us grant that the invisible sign can be apprehended, or admit the possibility of getting at the truth through the visible sign; still even they will admit their inability to preserve in due proportion what they call the "blending" of the signs in |192 these positions, for it often happens that the influence of a malignant star which appears is more or less weakened by the aspect of a more benign one; and again, that the weakening of the influence of the malignant star by the aspect of the benign one is hindered, because of some particular position and relation of the other, though it is indicative of evil. And I think that any one who studies the passages must despair of understanding such matters, inasmuch as the knowledge is not disclosed to men, but at the most only goes as far as the indication of events. And any one who has had actual experience will know that speakers and writers more frequently fail than succeed in their guesses at the truth. Wherefore Isaiah, believing that these things cannot be discovered by men, says to the daughter of the Chaldeans, who above all others were professors of the art, "Let now the astrologers, the star-gazers, stand up and save thee; let them tell thee what shall come upon thee." We are thus taught that the most learned in these matters cannot show beforehand what the Lord intends to bring upon every nation.