Begotten in us by things themselves, concepts are born reformers that never lose touch with reality. Pure ideas, on the other hand, are born within the mind and from the mind, not as intellectual expressions of what is, but as models, or patterns, of what ought to be; hence they are born revolutionists. And this is the reason why Aristotle and Aristotelians write books on politics, whereas Plato and Platonists always write Utopias.In the Chapter 3, he blames the philosophy of William of Ockham for introducing skepticism in the study of Aristotelian philosophy in the fourteenth century. Ockham’s philosophy took deep root in the European universities and led the scholastic philosophers on the straight road to scepticism.
Scholastic philosophers then began to mistrust their own principles, and mediaeval philosophy broke down; not for want of ideas, for they still were there; or for want of men, for there never were more brilliant intelligences than at the time of that glorious sunset; mediaeval philosophy broke down when, having mistaken philosophy for reality itself, the best minds were surprised to find reason empty and began to despise it.