"The necessity of ratiocination by symbols does carry in its train a tendency to mysticism from which even the keenest intellects cannot always free themselves. ...[footnote:] Some thinkers have spoken of, or alluded to, a certain 'reaction of language upon thought' which results in error or confusion... It is to this kind of illusion or, to... the mental attitude which makes it possible, that I refer when I speak of mysticism, the mystical tendency or bias."