Dk WHEWELL, ON PLATO'S SURVEY OF THE SCIENCES. 585 



and I may be wrong: but I have no notion of any science which makes the mind look upwards, 

 except a science which is about the permanent and the invisible. It makes no difference, as to 

 that matter, whether a man gapes and looks up or shuts his mouth and looks down. If a 

 man merely look up and stare at sensible objects, his mind does not look upwards, even if he 

 were to pursue his studies swimming on his back in the sea." 



The Astronomy, then, which merely looks at phenomena does not satisfy Plato. He wants 

 something more. What is it ? as Glaucon very naturally asks. 



Plato then describes Astronomy as a real science (§11). "The variegated adornments 

 which appear in the sky, the visible luminaries, we must judge to be the most beautiful and 

 the most perfect things of their kind : but since they are mere visible figures, we must. suppose 

 them to be far inferior to the true objects ; namely, those spheres which, with their real 

 proportions of quickness and slowness, their real number, their real figures, revolve and carry 

 luminaries in their revolutions. These objects are to be apprehended by reason and mental 

 conception, not by vision." And he then goes on to say that the varied figures which the skies 

 present to the eye are to be used as diagrams to assist the study of that higher truth ; just as 

 if any one were to study geometry by means of beautiful diagrams constructed by Daedalus or 

 any other consummate artist. 



Here then, Plato points to a kind of astronomical science which goes beyond the mere 

 arrangement of phenomena: an astronomy which, it would seem, did not exist at the time 

 when he wrote. It is natural to inquire, whether we can determine more precisely what kind 

 of astronomical science he meant, and whether such science has been brought into existence 

 since his time. 



He gives us some further features of the philosophical astronomy which he requires. "As 

 you do not expect to find in the most exquisite geometrical diagrams the true evidence of 

 quantities being equal, or double, or in any other relation : so the true astronomer will not 

 think that the proportion of the day to the month, or the month to the year, and the like, are 

 real and immutable things. He will seek a deeper truth than these. We must treat 

 Astronomy, like Geometry, as a series of problems suggested by visible things. We must 

 apply the intelligent portion of our mind to the subject." 



Here we really come in view of a class of problems which astronomical speculators at 

 certain periods have proposed to themselves. What is the real ground of the proportion of 

 the day to the month, and of the month to the year, I do not know that any writer of great 

 name has tried to determine : but to ask the reason of these proportions, namely, that of the 

 revolution of the earth on its axis, of the moon in its orbit, and of the earth in its orbit, 

 are questions just of the same kind as to ask the reason of the proportion of the revolutions 

 of the planets in their orbits, and of the proportion of the orbits themselves. Now who has 

 attempted to assign such reasons ? 



Of course we shall answer, Kepler : not so much in the Laws of the Planetary motions 

 which bear his name, as in the Law which at an earlier period he thought he had discovered, 

 determining the proportion of the distances of the several Planets from the Sun. And, 

 curiously enough, this solution of a problem which we may conceive Plato to have had in his 

 mind, Kepler gave by means of the Five Eegular Solids which Plato had brought into notice, 

 and had employed in his theory of the Universe given in the Timceus. 



75—2 



