[Philosophers came to be divided] into two camps: those who claimed that man
obtains his knowledge of the world by deducing it exclusively from concepts,
which come from inside his head and are not derived from the perception of
physical facts (the Rationalists)—and those who claimed that man obtains his
knowledge from experience, which was held to mean: by direct perception of
immediate facts, with no recourse to concepts (the Empiricists). To put it more
simply: those who joined the [mystics] by abandoning reality—and those who
clung to reality, by abandoning their mind.