CLASSICAL ANTIQUITY, MIDDLE AGES II 



From the fragments of his writings a number of general principles have been 

 gathered which are characteristic of his point of view; some of them sound 

 surprisingly like modern natural science. 



Out of nothing comes nothing; nothing which is can be reduced to 

 nothing. All change is merely an aggregation or separation of parts. 



Nothing happens by chance or intention, everything through cause and 

 of necessity. 



There is nothing but the atoms and space; all else is an impression of the 

 senses. 



The atoms are infinite in number and shape. Their movement is eternal; 

 in endless space they impinge upon one another, thereby producing vortices 

 out of which worlds arise, only again to perish. All the qualities of matter 

 are due to the shape, size, number, and motion of the atoms of which it is 

 composed. The atoms possess no other qualities than those mentioned above. 

 The soul consists of the finest and most mobile atoms; they fill the body and 

 give it life; if they leave the body, death ensues. Fire likewise consists of 

 small mobile atoms. On the whole, Democritus seems to have shared Hera- 

 cleitus' idea of the mutual affinity of the soul and fire. The stars he considered 

 to be like the earth, but owing to their rapid motion they were fiery bodies. 

 He seems also to have observed the mountains in the moon. 



Biological knowledge of Democritus 

 Democritus has achieved important work in the science of biology and he is 

 here, as in many other directions, the finest of Aristotle's predecessors; how 

 much of his learning his successor borrowed we do not know, but there are 

 grounds for supposing that it was far more than posterity has ever guessed. 

 Without doubt he performed dissections of both the higher and the lower 

 animals and was the first to differentiate between them according to the 

 quality of the blood. The distinction between sanguiferous animals (verte- 

 brates) and bloodless animals, which was the principle of classification 

 adopted by Aristotle, originates from Democritus. In contrast to Aristotle he 

 believed that even the minutest animals possess perfected organs, although, 

 owing to their transparency, they are invisible to the human eye. In the 

 embryonic development the external organs arise first and the internal after- 

 wards. Many of Democritus' ideas we know only through Aristotle's po- 

 lemics against them, and in this respect modern research not seldom proves 

 Democritus right. For instance, he considers that the spider's web is pro- 

 duced from inside its body while Aristotle maintained that it is cast-off skin. 

 The sterility of the mule he seeks to explain by assuming a contraction of its 

 uterus. The construction and functions of the human body, however, were 

 naturally the main object of his studies. He conceives man to be a world in 

 miniature, a microcosm in ^ which every kind of atom is represented. He re- 

 gards the brain as the organ of thought, the heart as that of courage, and 



