Sentence:  Again , Henley 's attitude of defiance which colors his ideal of self mastery is far from characteristic of a Stoic thinker like Marcus Aurelius , whose gentle acquiescence is almost Christian , comparable to the patience expressed in Milton 's sonnet on his own <WSD>blindness</WSD> . 
Meaning of the word marked with <WSD> tags:  the state of being blind or lacking sight