ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

THREE GREAT NAMES 29
the Sun, though he would not venture to say how they actually
moved.¹ But what is more important, he declared the motion of
a planet on an epicycle to be contrary to physical principles, be-
cause there are only three motions possible in this world : around
its centre, or towards it, or away from it; while he also main-
tained that according to Aristotle circular motion can only take
place round a real, central body.² Though Aristotle in reality
did not object to epicyclic motion with a mathematical point as
centre, for the simple reason that it had not been proposed when
he wrote, while, as we have seen, his moving principle had noth-
ing to do with the centre of motion, it is easy to see that Ibn
Badja's real difficulty was the same which afterwards produced so
many obstacles to the advance of science in Europe : whatever
could not be found in Aristotle's book must be unworthy of notice.
According to Maimonides (who, however, makes the reservation
that he had not heard it from disciples), Ibn Badja constructed a
system of his own, in which he only admitted excentric circles but
no epicycles. We are not given any particulars as to this system
but there can hardly be any doubt that its author confined himself
to generalities and did not attempt to represent phenomena like
the lunar inequalities by it. Maimonides remarks that there is
nothing gained by Ibn Badja's reform, since the excentric hypothe-
sis is as objectionable as the epicyclic one, as it also supposes
motion round an imaginary point outside the centre of the Earth.
The centre of the excentric, on which the Sun is supposed to
move, is outside the convexity of the lunar sphere and inside the
concavity of that of Saturn's excentric is between the spheres of
Mars and Jupiter. He adds that the revolution of a number of
concentric spheres around a common axis is conceivable, but not
the revolution round different axes inclined to each other, as the
spheres would disturb each other unless there are other spherical
bodies between them. This attempt to revive and modify the sys-
tem of (movable ?) excentrics did, therefore, not mend matters.³

1. Rabbi Mosis Majemonidis Liber . . . Doctor Perplexorum. Basileæ, 1629,
   Pars II. cap. IX.
2. Ibid., Pars II. cap. XXIV.
3. Maimonides also remarks (in the same chapter) that the supposed inclina-
   tions of Mercury and Venus in the Ptolemaic system are difficult or
   impossible to comprehend or imagine as really existing. Therefore, if what
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