Why did the author say that beginning to write felt like the “white, glaring, pupilless eyes of a blank page” glaring at him ?

During editing and proofreading, you do not need to

Drag the tiles to the correct boxes to complete the pairs. match these vocabulary words taken from great astronomers with their definitions. to come between two things, to interrupt the capacity to reason, judge, and act intelligently to form an opinion without strong evidence relating to the sky conjecture arrowright interpose arrowright celestial arrowright sagacity arrowright

Which fits best in the empty box above?