l!24 DANIEL A. CALLUS 



Thomas Aquinas who gave to the problem of the unity of sub- 

 stantial form its full significance. It is equally agreed that the 

 question cannot have originated with him, since it was current 

 in the schools as early as the first decades of the thirteenth 

 century, though, it is true, it then turned on a single instance, 

 namely whether the nutritive, the sensitive and the rational are 

 in man one soul, one substance, or three distinct souls or sub- 

 stances. (We have already observed that to say substance is 

 the same as saying form) . Further, it should be admitted that 

 many of the masters, who held that the three principles are in 

 man not only one soul, but also one substance, did not fully 

 grasp all its implications. Albert the Great was, perhaps, the 

 first to see the general and wider principles involved; yet he 

 too neither stressed the point nor deduced all the logical con- 

 clusions. With Aquinas, on the contrary, the debate entered a 

 new phase. Refusing to regard it merely as a psychological 

 theory, he considered it as fundamentally metaphysical, based 

 on the principle of contradiction; he thus gave it stability, uni- 

 versality and full value. Since it is essentially metaphysical, it 

 concerns the total range of matter-form composites, without 

 exception, holding good not only in psychology, but also in 

 logic, in the philosophy of nature and by inference in theology 

 as well. It is precisely here that Aquinas' original contribution 

 to the problem lies. Still, granted that St. Thomas' predecessors 

 and contemporaries, chiefly because of their somewhat imper- 

 fect grasping of metaphysical principles, did not clearly per- 

 ceive all the issues involved, the fact remains that the problem 

 itself, in its psychological aspect, had already been discussed 

 and propounded in the schools of Paris and Oxford for at 

 least half a century before St. Thomas' time. And if in reality 

 there were two contrary opinions, one must have been in sup- 

 port of plurality of substances, or forms, and the other in sup- 

 port of the unity of substance, or form. There is no alternative 

 position. 



The aim of this paper is not to discuss in detail the philo- 

 sophical issues of the problem, but to attempt to trace its 



