78 THE HISTORY OF BIOLOGY 



into three "kingdoms," those of nature, grace, and blessedness. In the first 

 dwell all men; the two latter are attainable only by members of the Church. 

 Knowledge of nature, therefore, even the heathen may acquire, and no 

 heathen has possessed deeper insight in this respect than Aristotle; he has 

 explored the kingdom of nature with unexcelled wisdom. Consequently the 

 Christian researcher may safely rely upon his explanation of nature and need 

 not engross himself in the subject — all the less so as the kingdoms of grace 

 and blessedness are open to him, the former in this life, the latter in the 

 eternal hereafter. In these circumstances the thinkers of the Middle Ages 

 devoted but little attention to natural-scientific research; they contented 

 themselves with the writings of Aristotle, which were closely commented 

 upon, even down to the smallest detail, without any effort's being made to 

 develop their subject-matter by actual investigation. There is a well-known 

 story of how the learned ecclesiastics disputed as to how many teeth the 

 horse should have according to Aristotle, instead of looking into the mouth 

 of a live horse to see for themselves. So much the more to the point were the 

 Aristotelean problems regarding the relation of ideas to reality; here the 

 dispute waxed hot between the realists, who believed that ideas existed 

 before things, and the nominalists, who declared that ideas exist only in 

 things. The view of the former was eventually given official sanction, but 

 their opponents refused to give in and so played their part in undermining 

 the reputation of the High-Church philosophy towards the end of the Middle 

 Ages. 



There are no biological writings proper dating from the earlier Middle 

 Ages. The descriptive work on animals, the Physiologus, which is mentioned 

 in all zoological histories, can indeed hardly be included in this category; it 

 consists of a collection of edifying stories relating to the animal world, 

 intended to serve as examples for quotation in sermons and gathered together 

 from all quarters. Probably it dates from later antiquity, which produced 

 many such collections, as, for instance, that made by i^lianus mentioned 

 above. The Physiologus, which was an anonymous treatise revised and issued 

 in various editions, had a surprisingly wide circulation; it was translated 

 into Ethiopian, Icelandic, and most languages existing between these bor- 

 derlands of Christian culture. It abounds in fantastic stories; a number of 

 them have survived even to the present day. 



Even in the Middle Ages, however, there existed people who had a 

 broader view of nature and a deeper interest in the life that stirs therein than 

 had the ecclesiastical legend-writers. Interesting evidence of this is to be 

 found in a treatise dating from about 11 50 entitled Physica, written by the 

 nun HiLDEGARD,of Bingen on the Rhine. The book contains notes on animals, 

 plants, and stones and on the benefit that man can derive from them. It is 

 entirely popular in style and without any pretension to learning, and for 



