This discourse on Sotillo, which seems meaningless to Decoud, is perfectly in keeping with Nostromo's mindset. To him, "sheer desperation," meaning integrity of character, is the deciding factor in the adventure: he is ready to sink the lighter, stab Decoud and die if necessary to preserve his unblemished reputation. He is trying to convince himself that Sotillo has no such integrity, invoking the discrepancy between his public and private behavior.