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 Omnia quse nobis longe confusa videntur 



I Bt velut in viridi candor nonsistere 

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



quare, 



Omnia cum rerum primordia sint in motu, 2 an,;, morp rlofim'tp ovnrpwinn is 



Summa tamen summa videatur stare I . 1 ls more detimte expression is 



quiete, entirely a question of mathematics. 



It is interesting to note how Le 

 Sage, in his ' Lucrece Neutonien ' 

 (Berlin Acad., 1782), "argues that 



Prseterquam siquid proprio dat corpore 



motus. 

 Omnis eniin longe nostris ab sensibus 



infra 

 Primorura natura jacet ; quapropter, ubi 



if Epicurus had had but a part of 



! the geometrical knowledge of his 



Cernere jam nequeas, motus quoque sur- 



pere debent ; 

 Prtesertim cum, quae possimus cernere, 



celent 

 Ssepe tamen motus spatio diducta lo- 



corum. 



Nam ssepe in colli tondentes pabula Iseta 

 Lanigerae reptant pecudes quo quamque 



vocantes 



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 " 

 Invitant herbse gemmantes rore recenti, ,-,, (T ,. , , .- ,-> 



Et satiati agni ludunt blandeque corus- (Munro, 'Lucretius, vol. 11. p. 13o). 

 cant ; I Lionardo da Vinci (1452-1519) says : 



