THE BELFAST ADDRESS. 139 



molecules. 2. Nothing happens by chance; every oc- 

 currence has its cause, from which it follows by neces- 

 sity. 3. The only existing things are the atoms and 

 empty space; all else is mere opinion. 4. The atoms 

 are infinite in number and infinitely various in form; 

 they strike together, and the lateral motions and whirl- 

 ings which thus arise are the beginnings of worlds. 



5. The varieties of all things depend upon the varie- 

 ties of their atoms, in number, size, and aggregation. 



6. The soul consists of fine, smooth, round atoms, like 

 those of fire. These are the most mobile of all: they 

 interpenetrate the whole body, and in their motions 

 the phenomena of life arise. 



The first five propositions are a fair general state- 

 ment of the atomic philosophy, as now held. As re- 

 gards the sixth, Democritus made his finer atoms do 

 duty for the nervous system, whose functions were then 

 unknown. The atoms of Democritus are individually 

 without sensation; they combine in obedience to me- 

 chanical laws; and not only organic forms, but the 

 phenomena of sensation and thought, are the result of 

 their combination. 



That great enigma, 'the exquisite adaptation of one 

 part of an organism to another part, and to the condi- 

 tions of life,' more especially the construction of the 

 human body, Democritus made no attempt to solve. 

 Empedocles, a man of more fiery and poetic nature, in- 

 troduced the notion of love and hate among the atoms, 

 to account for their combination and separation; and 

 bolder than Democritus, he struck in with the pene- 

 trating thought, linked, however, with some wild 

 speculation, that it lay in the very nature of those 

 combinations which were suited to their ends (in other 

 words, in harmony with their environment) to main- 

 tain themselves, while unfit combinations, having no 

 89 



