Sentence:  Argiento had been trained so rigorously by the Jesuits that Michelangelo <WSD>was</WSD> unable to change his habits : up before dawn to scrub the floors , whether they were dirty or not ; water boiling on the fire for washing laundry every day , the pots scoured with river sand after each meal . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)