To the arguments against nativities that men die the same death who were not born at the same time and that men who are born at the same time are not identical in character or fortune Sextus Empiricus adds the derisive question whether a man and an ass born in the same instant would suffer exactly the same destiny. Ptolemy would of course reply that while the influence of the stars is constant in both cases it is variably received by men and donkeys; and Sextus’s query does not show him very well versed in astrology. He mentions the obstacle of free will to astrological theory but does not make very much of it. The chief point which he makes is that even if the stars do rule human destiny, their effect cannot be accurately measured. He lays stress on the difficulty of exactly determining the date of birth or of conception, or the precise moment when a star passes into a new sign of the zodiac. He notes the variability and unreliability of water-clocks. He calls attention to the fact that observers at varying altitudes as well as in different localities would arrive at different conclusions. Differences in eyesight would also affect results, and it is difficult to tell just when the sun sets or any sign of the zodiac drops below the horizon owing to reflection and refraction of rays. Sextus thus leaves us somewhat in doubt whether his objections are to be taken as indicative of a spirit of captious criticism towards an art, the fundamental principles of which he tacitly recognizes as well-nigh incontestable, or whether he is simply trying to make his case doubly sure by showing astrology to be impracticable as well as unreasonable. In any case we shall find his argument that the influence of the stars cannot be measured accurately repeated by Christian writers. [Sidenote: _Lucius_ or _The Ass_: is it by Lucian?]