4 SCIENTIFIC THOUGHT. 



mena and properties of natural objects, and the higher 

 ethical problem of fixing upon that which is lastingly 

 real and important in the continuous change of sensation 

 and opinion. The latter formed the central interest of 

 that course of reasoning which began with Socrates and 

 culminated in Plato and Aristotle ; the former was the 

 problem of natural philosophy of which Epicurus and 

 Lucretius stand out as the great representatives. In 

 a well-known passage of the second book of his great 

 poem, Lucretius explains the apparent rest of natural 

 things by the simile of a flock of lustily dancing sheep, 

 which at a distance looks like a white spot on a green 

 hillside. 1 This tendency of philosophic reasoning to see 

 motion where common-sense only sees rest, to reduce 

 theoretically the apparently permanent properties of 

 things to a play of intricate but imperceptible modes 

 of motion, has governed still more markedly modern 

 scientific thought. I shall comprise all efforts to give 

 more definite 2 expression to this general idea under 



1 ' De Natura Rerum,' ii. 308 Orania quse nobis longe confusa videntur 



I Et velut in viridi candor consistere 

 "Illud in his rebus non est mirabile, ; colli." 



quare, 



more definite expression is 

 quiete, entirely a question of mathematics. 



Prseterquam siquid proprio dat corpore 



motus. 

 Oinnis enim longe nostris ab sensibus 



infra 

 Prime-rum natura jacet ; quapropter, nbi 



ipsa 

 Cernere jam nequeas, motus quoque sur- 



pere debent ; 

 Prsesertim cum, quse possimus cernere, 



celent 

 Sfepe tamen motus spatio diducta lo- 



corum. 



Nam ssepe in colli tondentes pabula Iseta 

 T,anigeree reptant peeudes quo quamque 



vocantes 



Invitant herbte gemmantes rore recenti, 

 Et satiati agui ludunt blandeque corus- 



cant ; 



It is interesting to note how Le 

 Sage, in his ' Lucrece Neutonien ' 

 (Berlin Acad., 1782), "argues that 

 if Epicurus had had but a part of 

 the geometrical knowledge of his 

 contemporary Euclid, and concep- 

 tions of cosmography the same as 

 those of many then living, he might 

 have discovered the laws of uni- 

 versal gravity, and not only the 

 laws, but, what was the despair of 

 Newton, its mechanical cause " 

 (Munro, 'Lucretius,' vol. ii. p. 135). 

 Lionardo da Vinci (1452-1519) saya : 



