THE BELFAST ADDRESS 



not necessary to conceive any other 

 vegetative or sensitive soul, nor any other 

 principle of motion or of life, than the blood 

 and the spirits agitated by the fire which 

 burns continually in the heart, and which 

 is in nowise different from the fires exist- 

 ing in inanimate bodies." Had Descartes 

 been acquainted with the steam-engine, 

 he would have taken it, instead of a fall 

 of water, as his motive power. He would 

 have shown the perfect analogy which 

 exists between the oxidation of the food 

 in the body and that of the coal in 

 the furnace. He would assuredly 

 have anticipated Mayer in calling the 

 blood, which the heart diffuses, " the oil 

 of the lamp of life," deducing all animal 

 motions from the combustion of this oil, 

 as the motions of a steam-engine are 

 deduced from the combustion of its coal. 

 As the matter stands, however, and con- 

 sidering the circumstances of the time, 

 the boldness, clearness, and precision 

 with which Descartes grasped the prob- 

 lem of vital dynamjcs constitute a 

 marvellous illustration of intellectual 

 power. 1 



During the Middle Ages the doctrine 

 of atoms had to all appearance vanished 

 fr<$n discussion. It probably held its 

 ground among sober-minded and thought- 

 ful men, though neither the church nor 

 the world was prepared to hear of it with 

 tolerance. Once, in the year 1348, it 

 received distinct expression. But re- 

 tractation by compulsion immediately 

 followed; and, thus discouraged, it 

 slumbered till the seventeenth century, 

 when it was revived by a contemporary 

 and friend of Hobbes of Malmesbury, 

 the orthodox Catholic provost of Digne, 

 Gassendi. But, before stating his rela- 

 tion to the Epicurean doctrine, it will be 

 well to say a few words on the effect, as 

 regards science, of the general introduc- 

 tion of monotheism among European 

 nations. 



" Were men," says Hume, " led into 

 the apprehension of invisible intelligent 



1 See Huxley's admirable Essay on Descartes. 

 Lay Sei-mons, pp. 364, 365. 



power by contemplation of the works of 

 Nature, they could never possibly enter- 

 tain any conception but of one single 

 Being, who bestowed existence and order 

 on this vast machine, and adjusted all 

 its parts to one regular system." Refer- 

 ring to the condition of the heathen, who 

 sees a god behind every natural event, 

 thus peopling the world with thousands 

 of beings whose caprices are incalculable, 

 Lange shows the impossibility of any 

 compromise between such notions and 

 those of science, which proceeds on the 

 assumption of never-changing law and 

 causality. " But," he continues, with 

 characteristic penetration, " when the 

 great thought of one God, acting as a 

 unit upon the universe, has been seized, 

 the connection of things in accordance 

 with the law of cause and effect is not 

 only thinkable, but it is a necessary con- 

 sequence of the assumption. For when 

 I see ten thousand wheels in motion, 

 and know, or believe, that they are all 

 driven by one motive power, then I 

 know that I have before me a mecha- 

 nism, the action of every part of which 

 is determined by the plan of the whole. 

 So much being assumed, it follows that 

 I may investigate the structure of that 

 machine, and the various motions of its 

 parts. For the time being, therefore, 

 this conception renders scientific action 

 free." In other words, were a capricious 

 god at the circumference of every wheel 

 and at the end of every lever, the action 

 of the machine would be incalculable by 

 the methods of science. But the actions 

 of all its parts being rigidly determined 

 by their connections and relations, and 

 these being brought into play by a 

 single motive power, then, though this 

 last prime mover may elude me, I am 

 still able to comprehend the machinery 

 which it sets in motion. We have here 

 a conception of the relation of Nature 

 to its Author, which seems perfectly 

 acceptable to some minds, but perfectly 

 intolerable to others. Newton and 

 Boyle lived and worked happily under 

 the influence of this conception ; Goethe 

 rejected it with vehemence, and the same 



