Sentence:  In recent years , we have come increasingly to recognize that ideas have a history and that not the least important <WSD>chapters</WSD> of this history have to do with thematic or conceptual aspects of literature and the arts , although these aspects should be studied in conjunction with the history of philosophy , of religion , and of the sciences . 
Meaning of the word marked with <WSD> tags:  any distinct period in history or in a person's life