80 DISTINCTION BETWEEN ANIMALS, 



ner from inanimate things to animals, through forms of hfe 

 which are not animals, in such a way that one class seems 

 to differ very little from another in the part where they 

 border on each other." * 



These ideas were not altogether original, but had been 

 partly foreshadowed by other philosophers. Empedocles, 

 Democritus, and others considered that plants had sensation 

 and cognition, as will be seen later in Chapter vii. They 

 believed, in fact, that the vital principle of plants was 

 nearly the same as that of animals. 



In the above passages from Aristotle's H. A. and P. A. 

 the word a-^ux^v is employed several times. It signifies 

 something without -^oxn, which may be translated " vital 

 principle," although it is doubtful whether there is any 

 English word or phrase which exactly corresponds with the 

 meaning intended by Aristotle. This vital principle is 

 described chiefly in his De Anima. It is that active 

 principle which, in association with bodies, organized in 

 some way, gives rise to the phenomena of life. The word 

 " organized " is used here only for the sake of convenience ; 

 taken without qualification, it represents a knowledge of 

 the constitution of matter far more advanced than Aristotle's 

 ideas on that subject. He considered the vital principle to 

 be related to living bodies in a manner comparable with the 

 relationship of Form to Matter, or Sight to the Eye, and 

 says that if an eye were a living being, then sight would be 

 its vital principle.! He contemplated several kinds of vital 

 principle, manifested by functions of different degrees of 

 dignity or importance, the chief being : (1) the Nutritive ; 

 (2) the Sentient, and (3) the Intellectual. Whatever has 

 one of these principles is said to live, and Aristotle assigned 

 only one to a form of life, because the sentient includes the 

 nutritive, and the intellectual includes both the nutritive 

 and the sentient vital principles. All forms of life have the 

 nutritive vital principle at least. 



In his contemplations of forms of life, Aristotle con- 

 sidered the vital principle to be more important than the 

 matter associated with it, yet the constitution of this matter 

 had to satisfy some conditions to enable the vital principle 

 to be associated therewith. He does not seem to suggest 

 that the vital principle could be associated with a sculptured 

 block of marble or an image cast from bronze. He believed, 



* P. A, iv. c. 5, 681a. f De Anima, ii. c. 1, 4126. 



