ANCIENT AND MEDIAEVAL BELIEFS 7 



warmth '. Thus, in spontaneous generation, decaying 

 materials do not on their own give rise to Hfe ; they are 

 brought to life under the influence of the light of the sun 

 which gives ' psychic warmth '. 



The views of Aristotle exerted an enormous influence on 

 the whole subsequent history of the problem of the origin 

 of life. Aristotle, with his undisputed authority, supported 

 the results of direct, naive observation, and for many 

 centuries ahead prejudiced further study of spontaneous 

 generation. All the later philosophical schools, both Greek 

 and Roman, completely shared the opinion of Aristotle on 

 the possibility of spontaneous generation of living beings. 

 Moreover, as time went on the theoretical basis of the 

 ' phenomenon ' took on a more and more idealistic, indeed 

 even mystical, character. 



A whole series of writings, from the 3rd and 2nd centuries 

 B.C., contain numerous tales and ' miraculous stories ' of 

 * plagues of lice ' in which the juices of the human body are 

 changed into parasites, of the appearance of worms and 

 insects from rotting materials, of crocodiles from the mud of 

 the Nile, and so forth. Concerning such matters, the most 

 authoritative philosophical school of that time, the Stoics, 

 taught that animals and plants originate as a result of the 

 activity of ' engendering force ' which is a property of 

 pneiima. 



From the later Stoics this view obtained a wide circula- 

 tion in both East and West, through a number of 

 philosophers and writers, particularly the much-travelled 

 Poseidonius. It thus obtained general recognition at the 

 beginning of our own era. In scientific treatises, in political 

 pronouncements and in artistic productions of that period 

 we meet continually with descriptions of various cases of 

 spontaneous generation. We find them in the works of 

 Cicero, of the famous geographer Strabo, of the versatile 

 scholar Philo of Alexandria, of the historian Diodorus 

 Siculus, of such poets as Virgil and Ovid, as well as in the 

 works of the later WTiters Seneca, Pliny, Plutarch and 

 Apuleius.^^ 



The idealistic character of the teachings concerning spon- 

 taneous generation was clearly expounded by the neo- 



