Decoud, seeking a validation of his individual worth, protests that he helped keep the lighter afloat, i.e., he made a contribution to the preservation of society, much like he did in a larger sense with his political plan. Nostromo responds that he would have rather sunk alone and been sure of his reputation -- i.e., his dream-ideal is stronger than his desire for life -- so it doesn't matter what practical contribution Decoud made. Decoud's individuality receives no validation there.