Francis Patrick Duffy

“ A further and most important step is taken when the mind reaches the stage where it can handle its abstractions such as extension, motion, species, being, cause, as a basis for science and philosophy, in which, to a certain extent at least, the abstracted concepts are manipulated like the symbols in algebra, without immediate reference to the concrete. ”

“ The simplest-seeming things are complex, i.e. they have various attributes; and the process of abstraction begins with sensation, as sight perceives certain qualities; taste, others; etc. From the dawn of intelligence the activity progresses rapidly, as all of our generalizations depend upon the abstraction from different objects of some phase, or phases, which they have in common. ”

“ A widely prevalent view, best represented by the Associationist school, is that general ideas are formed by the blending or fusing of individual impressions. The most eminent Scholastics, however, following Aristotle, ascribe to the mind in its higher aspect a power (called the Active Intellect) which abstracts from the representations of concrete things or qualities the typical, ideal, essential elements, leaving behind those that are material and particular. ”