72. THE HISTORY OF BIOLOGY 



and pursuits, he was imprisoned, stripped of his honours, and banished to 

 a village near Cordova inhabited by Jews. Fortunately the ruling prince who 

 committed this act of injustice died a year or two afterwards and his son 

 and successor immediately repaired it; Averroes was recalled to court and 

 resumed his honours, but died shortly after, in 1198. 



As a natural philosopher Averroes followed Aristotle, and his principal 

 work takes the form of commentaries on Aristotle's writings. Averroes's 

 standpoint is, however, far more than that of his predecessors and even than 

 that of any other mediaeval philosopher, independent of his model. He bases 

 his philosophy on the latter' s ideas, but he develops them further on his 

 own account. In particular he studied the relation between potentiality and 

 reality in nature. Aristotle considered that marble is a potentiality, which 

 becomes reality when a statue is made out of it, and he consistently applied 

 this method to life in nature — the seed, the embryo, is a potentiality; the 

 plant, the animal, reality. Averroes argued in opposition to this view that 

 nothing in nature is potential that does not exist in reality, in however un- 

 developed and therefore disguised a form it may be; the plant already exists 

 in the seed, in however undeveloped a state, just like the animal in the embryo. 

 The simile of the marble and the statue Averroes considers inapplicable where 

 nature is concerned; at best the simile would be admissible if the statue were 

 to be found already shaped in the veins of the unsculptured block. By this 

 method of speculation Averroes has carried science a long step nearer the 

 present-day conception of natural evolution; Aristotle's purely abstract 

 idea of potentiality is here replaced by something which approaches far 

 nearer to our idea of energy. Averroes was the last great Arabic philosopher 

 and the greatest natural philosopher of the Middle Ages; if anyone is worthy 

 to be called the Aristotle of the Middle Ages, it is he. He resembles his pro- 

 totype not only in the fact of his having lived in a decadent era and been 

 subjected to religious persecution, but also in the fact that no one for cen- 

 turies succeeded in developing his ideas further. Shortly after his death 

 Arabic science succumbed to religious intolerance, while even the Christian 

 schoolmen, who closely studied and highly honoured the Arabic philoso- 

 pher,^ saw in him only the interpreter of Aristotle and were not capable of 

 realizing the great advance he made towards a more real conception of na- 

 ture. He has not, however, been without influence; in the Middle Ages the 

 opponents of ecclesiastical philosophy gathered round his name, and the 

 ideas he evoked can thus be traced through the ages until they find confirma- 

 tion in the natural science of our own day. 



Arabic literature has produced, besides the natural philosophers men- 

 tioned, several authors who have dealt with zoology in a more restricted 



^ During his imaginary wanderings in the underworld Dance sees Averroes in the court 

 of the heathen by the side of Aristotle and other philosophers of antiquity. 



