Sentence:  It is to say rather , I believe , that he has brought to bear on the history , the traditions , and the lore of his region a critical , skeptical <WSD>mind</WSD> - the same mind which has made of him an inveterate experimenter in literary form and technique . 
Meaning of the word marked with <WSD> tags:  that which is responsible for one's thoughts and feelings; the seat of the faculty of reason