Again Decoud states clearly the novel's theme of the necessary yet destructive dream-ideal. What's more, to Mrs Gould he speaks openly of the divergence between Charles' "conception of things" and hers, emphasizing the subjective nature of the dream-ideal. However, this reiteration contains a very revealing addition: the phrase "or exist." It is the clearest statement of what is implied by whole book, and especially by Decoud's suicide: that the dream-ideal is necessary not merely for action, but for existence. I.e., some organizing principle, by definition illusory, is necessary for us to live at all in a world of meaningless chaos.

By "fairy tale" Decoud means only another denuniciation of the dream-ideal. But in the context of speaking to Mrs Gould -- whom the novel compares to a fairy several times -- the line takes on a greater meaning, reminding us that Charles would literally "not believe his own motives" (his dream-ideal of materialist progress) unless he associated them with Emily's altruism. For more on this see my earlier note on their allegorical marriage.