Sentence:  Chewing it over with his colleagues and in his own mind , he reaches a tentative identification of the question - tentative because it may change as he explores it <WSD>further</WSD> and because , if no tolerable answer can be found , it may have to be changed into one which can be answered . 
Meaning of the word marked with <WSD> tags:  to or at a greater extent or degree or a more advanced stage (`further' is used more often than `farther' in this abstract sense)