In the first place, the science demands the greatest study and a constant attention to a multitude of different points; and as all persons who are but imperfectly practised in it must necessarily commit frequent mistakes, it has been supposed that even such events as have been truly predicted have taken place by chance only, and not from any operative cause in nature. But it should be remembered that these mistakes arise, not from any deficiency or want of power in the science itself, but from the incompetency of unqualified persons who pretend to exercise it. And, besides this, the majority of the persons who set themselves up as professors of this science, avail themselves of its name and credit for the sake of passing off some other mode of divination; by that means defrauding the ignorant, and pretending to foretell many things which from their nature cannot possibly be foreknown; and consequently affording opportunities to more intelligent people to impugn the value even of such predictions as can rationally be made. The reproach, however, thus brought upon the science is wholly unmerited; for it would be equally just to condemn all other branches of philosophy, because each numbers among its professors some mischievous pretenders. Secondly, it is not attempted to be denied that any individual, although he may have attained to the greatest possible accuracy in the science, must still be liable to frequent error, arising out of the very nature of his undertaking, and from the weakness of his limited capacity in comparison with the magnitude of his object. For the whole theory of the quality of matter is supported by inference rather than by positive and scientific proof; and this is caused principally by the concretion of its temperament out of a multitude of dissimilar ingredients. And, although the former configurations of the planets have been observed to produce certain consequences (which have been adapted to configurations now taking place), and are, after long periods, and in a greater or less degree, resembled by subsequent configurations, yet these subsequent configurations never become exactly similar to those which have preceded them. For an entire return of all the heavenly bodies to the exact situation in which they have once stood with regard to the earth will never take place, or at least not in any period determinable by human calculation, whatever vain attempts may be made to acquire such unattainable knowledge.[22] The examples referred to for guidance being therefore not exactly similar to the existing cases to which they are now applied, it must naturally follow that predictions are sometimes not borne out by the events. Hence arises the sole difficulty in the consideration of events produced by the Ambient. For no other concurrent cause has been hitherto combined with the motion of the heavenly bodies; although the doctrine of nativities, particularly that part of it relating to