"no light without shadow"

a quote from the book i'm reading now:

"He taught me everything i know about photography, from the choice of a lens to the laborious process of developing. i never had any other teacher. ...now he is seventy-four years old... he is passionate about life, and blindness has not prevented him from continuing to survey the world. he has developed a kind of second sight. the way other blind people have someone to read to them, he has various helpers who observe and report to him. his students, his friends, and his children visit him every day and take turns describing what they've seen: a landscape, a scene, a face, an effect of light. they have to learn to observe very closely in order to endure his exhaustive interrogation. as as result their lives change; they can't any longer wander through the world in their old casual way because they have to see with the maestro's eyes."