And here we have a particularly explicit statement of the novel's theme: that the "immaterial" side of the world is the only "real" side, that things exist to us only insofar as they serve a guiding, interpreting dream-ideal.
The notion of the "stain" is one that will recur throughout the novel,
always in connection with the pure ideal coming into contact with reality and
being thereby corrupted. See Decoud's disparagement of Charles Gould for thinking
his "honesty unstained" ,
and Nostromo feeling as his fingers have received a "stain" from his
illicit silver ingots
.
See also Mrs Gould's critical line, "There was something inherent in the
necessities of successful action which carried with it the moral degradation
of the idea."
In Nostromo, purity is an aspect only of the immaterial dream-ideal;
any attempt to materialize it in the physical world leads to its degradation.