It's not until Book Three, until after Milton presents his heroic portrait of Satan and his heroic portrait of the fallen angels when he establishes the fact of his blindness.

直到第三卷弥尔顿呈现,他对撒旦和降落的天使们的英勇形象后,他才证实自己失明的事实。

耶鲁公开课 - 弥尔顿课程节选