338 PHYSICAL SCIENCE IN THE MIDDLE AGES. 



of considering such subjects, to which both Aristotle 

 and Plato had contributed, travelled in the opposite 

 direction, and endeavoured to discover how indi- 

 viduals were deduced from genera and species; 

 what was "the Principle of Individuation." This 

 was variously stated by different reasoners. Thus 

 Bonaventura 15 solves the difficulty by the aid of the 

 Aristotelian distinction of Matter and Form. The 

 individual derives from the Form the property of 

 being something, and from the Matter the property 

 of being that particular thing. Duns Scotus 16 , the 

 great adversary of Thomas Aquinas in theology, 

 placed the Principle of Individuation in " a certain 

 positive determining entity," which his school called 

 Hcecceity, or thisness. " Thus an individual man is 

 Peter, because his humanity is combined with Pe- 

 treityT The force of abstract terms is a curious 

 question, and some remarkable experiments in their 

 use had been made by the Latin Aristotelians before 

 this time. In the same way in which we talk of 

 the quantity and quality of a thing, they spoke of 

 its quiddity' 1 . 



We may consider the reign of mere disputation 

 as fully established at the time of which we are now 

 speaking ; and the only kind of philosophy hence- 

 forth studied was one in which no sound physical 

 science had or could have a place. The wavering 

 abstractions, indistinct generalizations, and loose 

 classifications of common language, which we have 

 15 Deg. iv. 573. 16 Ib. iv. 523. 17 Ib. iv. 494. 



