The Meaning of it in "The Death of Ivan Ilyich"

The meaning of "it" is very complex in the story "The Death of Ivan Ilyich" by Leo Tolstoy. The character that gives this word meaning is called Ivan llyich. Ivan llyich was a Russian judge and he realizes "it" when he became ill.
When Ivan Ilyich was becoming sick, many of the doctors came to check on him. Ivan had a problem with these doctors because they dodged the fact that Ivan was going to die. Ivan saw right through these physicians, knowing that they were clouding their diagnosis. To Ivan Llyich only one question was important: was his case serious or not? …