The debate about Nostromo's motives is, as usual, allegorically a debate about
the motives of the People -- the logical climax to the Separatist argument. Mrs
Gould was interested that Nostromo should side with the Europeans -- one apparent
gesture of Unity in a long Separatist day. The anti-materialist Mrs Gould rejects
Decoud's suggestion that the People are acting from motives of fortune-hunting.
And she ends with the ultimate damning indictment of Separatism: if everyone has
their own "interest," then no one can be trusted. By applying the argument
to Nostromo, it allegorically extends to all.