How does the use of the word "incoherent" in this excerpt of the last chapter of The Great Gatsby by F. Scott Fitzgerald contribute to the passage?
On the last night, with my trunk packed and my car sold to the grocer, I went over and looked at that huge incoherent failure of a house once more.
In everyday context, the word "incoherent" generally ranges in meaning from something that cannot be understood when it is spoken aloud (The boy's response to the demand was incoherent) to something that cannot be understood as written (The student's paper, while lengthy, was disorganized and the ideas were presented in an incoherent fashion). In the closing pages of Fitzgerald's novel The Great Gatsby, his final reflections on the "incoherent failure of a house" that was Jay Gatsby's have more to do with the confusion associated with the idealism of one's dreams (America's in general, and Gatsby's in particular) and the reality of the corruption of both.
Gatsby's home, his parties, the American dream, all of these things glittered like stars, were beautiful to contemplate and to describe. But beneath the surface, if one looked too closely, there was dishonesty, hedonism, even in some cases evil, lurking in and among this society. To look at Gatsby's home was to see a beautiful home owned by a man whose dreams, while attained by some admittedly illegal means, were still sincere and mostly informed by his love for a woman he had never forgotten. While one might argue that the home was a symbol of materialism and the corruption of the American dream, which it certainly was, one could also perhaps argue that the home was the symbol of a misguided, but heartfelt desire; therein lies the "incoherent" nature of the home, for it is full of contradictions.
The "incoherent failure of a house" was a metaphor for everything that was wrong with the "American Dream" in general, and Gatsby's dream in particular, right up to the day of the foul play that resulted in his death, an event that created the final scene of ugliness juxtaposed against the superficial beauty that surrounded it.