Sentence:  <WSD>Philosophy of mind</WSD>, paradoxically enough, became an interesting area of philosophy only when philosophers began to stop taking the notion of "mind" for granted and began asking whether it was a misleading locution. 
Meaning of the word marked with <WSD> tags:  The area of philosophy which studies the nature and functions of the mind, thought, and consciousness, with attention to such topics as perception, reasoning, belief, memory, will, and identity.