The pursuit of utopian socialism through wealth was of course Nostromo's own method, and his downfall. But I see a larger meaning of "weapons" here, relating to all conquest. That is, conquest must be met with conquest, dream-ideal with dream-ideal, the armies of the exploiters with the armies of the exploited, at every stage of human history. Nostromo, who attempted to escape the cycle and failed, has no answer to make.