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 qua nobis longe confusa videntur 



Et velut in viridi candor consistere 

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



quare, 



Omnia cum rerum primordia sint in motu, 2 m, HofinitP Pxnrpssioii ia 



Summa tamen summa videatur stare 



quiete, entirely a question of mathematics. 



Praterquam siquid proprio dat corpore It is interesting to note how Le 



Sage, in his ' Lucrece Neutonieu ' 

 (Berlin Acad., 1782), "argues that 

 if Epicurus had had but a part of 



, 5 P sa . i the geometrical knowledge of his 



Cernere jam nequeas, motus quoque sur- -r> ,., 



peredebent; contemporary Euclid, and concep- 



Prsesertim cum, qua; possimus cernere, : tions of cosmography the same as 



celent those of many then living, he might 



8eP comm en m tUS SPati dldUCta 10 ~ i have Discovered the laws of uni- 



Nam spe in colli tondentes pabula laeta versal gravity, and not only the 



Lanigerae reptant pecudes quo quamque laws, but, what was the despair of 



vocantes Newton, its mechanical cause " 



Invitant herbiie gemmantes rore recenti, /.. , T ,. , , .. , -\ 



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



cant ; i Lionardo da Vinci (1452-1519) says i 



Omnis enim longe nostris ab sensibus 



infra 

 Primorum natura jacet ; quapropter, ubi 



