THE EVOLUTION IDEA 113 



and unchangeable grounds of reason upon which the 

 world is regulated. Under the influence of the third 

 person of the Godhead, the potentialities of matter 

 are developed, out of which creatures take their 

 origin. In a retrogressive circle, all things return to 

 God. 



Here Erigena turned to Plato's conception of 

 final cause. 



Aquinas (1225-1274) 



Of much greater influence is the teaching of 

 Thomas Aquinas as late as the middle of the 

 thirteenth century, for he was and is one of the 

 highest authorities in the Church. He does not 

 contribute to the evolution idea but simply ex- 

 pounds the natural philosophy of Augustine: 



As to production of plants, Augustine holds a dif- 

 ferent view, . . . for some say that on the third day 

 plants were actually produced, each in his kind — a 

 view favored by the superficial reading of Scripture. 

 But Augustine says that the earth is then said to 

 have brought forth grass and trees causaliter; that 

 is, it then received power to produce them. ... In 

 those first days . . . God made creation primarily 

 or causaliter, and then rested from His work. 



Roger Bacon (1214-1294) 



The outstanding figure of the Middle Ages in 

 regard to the investigation of natural laws is. 



