 Rationalists, in contrast, argued that knowledge was by nature both abstract and deductively certain. Consider, for a moment, your sensory experiences: they are fluid, individualized, and permeated by the relativity borne of innumerable external conditions. How could a philosophical account of genuine knowledge—necessarily certain, self-evident, and unchanging—be derived using a method so besotted with sensorial flux? Knowledge must derive, rather, from inner concepts, which could be certain. Knowledge, then, is produced by an immaterial entity, mind, with a power to reason which is innate, and which stands logically independent of practical ends and the contingencies of one’s physical body.