In Chapter 2, why does Nick see himself as both on the outside and inside of the apartment?

Nick is quite drunk as he, Tom, Myrtle, and the others sit in the apartment and drink.  He would like to leave but feels he cannot; he tries to but “became entangled in some wild strident argument which pulled [him] back, as if with ropes, into [his] chair” (40). He feels as if everything going on in the apartment can be seen by strangers on the street, and that he is one of those strangers, so that he while he is a participant in this scene, he is also an observer of this.  All that he sees seems bizarre, without sense, and rather surrealistic or dreamlike: things happening without clear meaning. The sense of experiencing himself within and without a situation suggests a very modern view of the world, something that WEB Dubois would call a “double consciousness,” and it is brought about by doing something that is meaningless to him and knowing it is meaningless but doing it anyway. He is experiencing an intense alienation, feeling that he is an “insider” to all that is going on because he is part of the group simply by his presence, but he is also an “outsider” because he does not share the values or understand the dynamics. Nick's role as narrator involves this double view throughout:  he participates in the events while he also pulls his away to view them and report on them.