PLATO 
285 
heavenly bodies. The arrangement of' the stars in the heaven 
and their apparent movements are indeed wonderful and 
beautiful, but the observation of and the accounting for them 
falls far short of true astronomy. Before we can attain to 
this we must get beyond mere observational astronomy, ‘we 
must leave the heavens alone ’. The true science of astronomy 
is in fact a kind of ideal kinematics, dealing with the laws 
of motion of true stars in a sort of mathematical heaven of 
which the visible heaven is an imperfect expression in time 
and space. The visible heavenly bodies and their apparent 
motions we are to regard merely as illustrations, comparable 
to the diagrams which the geometer draws to illustrate the 
true straight lines, circles, &c., about which his science reasons; 
they are to he used as ‘ problems ’ only, with the object of 
ultimately getting rid of the apparent irregularities and 
arriving at ‘the true motions with which essential speed 
and essential slowness move in relation to one another in the 
true numbers and the true forms, and carry their contents 
with them ’ (to use Burnet’s translation of ra kvovra)} 
‘Numbers’ in this passage correspond to the periods of the 
apparent-motions; the ‘true forms’ are the true orbits con 
trasted with the apparent. It is right to add that according 
to one view (that of Burnet) Plato means, not that true 
astronomy deals with an ‘ ideal heaven ’ different from the 
apparent, but that it deals with the true motions of the visible 
bodies as distinct from their apparent motions. This would 
no doubt agree with Plato’s attitude in the Laws, and at the 
time when he set to his pupils as a problem for solution 
the question by what combinations of uniform circular revolu 
tions the apparent movements of the heavenly bodies can be 
accounted for. But, except on the assumption that an ideal 
heaven is meant, it is difficult to see what Plato can mean 
by the contrast which he draws between the visible broideries 
of heaven (the visible stars and their arrangement), which 
are indeed beautiful, and the true broideries which they 
only imitate and which are infinitely more beautiful and 
marvellous. 
This was not a view of astronomy that would appeal to 
the ordinary person. Plato himself admits the difficulty. 
1 Rep. vii. 529 c-530 c.