...then there is nothing but the "sadness of a sceptical mind," the self alone, knowing itself to be disconnected from its proper direction.

This is the novel's clearest statement that some sort of organizing illusion is necessary even to identify the objects of the physical world, that the most basic, sustaining level of thought is still an invalid fantasy to the skeptic. Compare above, where Nostromo in the dinghy "did not seem to know the gulf."