If the common mistake in empiricism is not to see the omnipresence of reason in thought, the mistake of rationalism is not to admit its variability and dependence, not to understand its natural life. Parmenides was the Adam of that race, and first tasted the deceptive kind of knowledge which, promising to make man God, banishes him from the paradise of experience. His sin has been transmitted to his descendants, though hardly in its magnificent and simple enormity. “The whole is one,” Xenophanes had cried, gazing into heaven; and that same sense of a permeating identity, translated into rigid and logical terms, brought his sublime disciple to the conviction that an indistinguishable immutable substance was omnipresent in the world. Parmenides carried association by similarity to such lengths that he arrived at the idea of what alone is similar in everything, viz., the fact that it is. Being exists, and nothing else does; whereby every relation and variation in experience is reduced to a negligible illusion, and reason loses its function at the moment of asserting its absolute authority. Notable lesson, taught us like so many others by the first experiments of the Greek mind, in its freedom and insight, a mind led quickly by noble self-confidence to the ultimate goals of thought. Such a pitch of heroism and abstraction has not been reached by any rationalist since. No one else has been willing to ignore entirely all the data and constructions of experience, save the highest concept reached by assimilations in that experience; no one else has been willing to demolish all the scaffolding and all the stones of his edifice, hoping still to retain the sublime symbol which he had planted on the summit. Yet all rationalists have longed to demolish or to degrade some part of the substructure, like those Gothic architects who wished to hang the vaults of their churches upon the slenderest possible supports, abolishing and turning into painted crystal all the dead walls of the building. So experience and its crowning conceptions were to rest wholly on a skeleton of general natures, physical forces being assimilated to logical terms, and concepts gained by identification of similars taking the place of those gained by grouping disparate things in their historical conjunctions. These contiguous sensations, which occasionally exemplify the logical contrasts in ideas and give them incidental existence, were either ignored altogether and dismissed as unmeaning, or admitted merely as illusions. The eye was to be trained to pass from that parti-coloured chaos to the firm lines and permanent divisions that were supposed to sustain it and frame it in.