A few days after Billy's death, the ship's purser and the surgeon discussed the event in the mess hall. The purser claims that the stillness of Billy's body during his execution is proof of Billy's remarkable will power. The surgeon, though, says that a body's movement while being hanged is the result of involuntary muscle spasms. Billy's stillness, then, was unintentional and no proof of extraordinary will power.
The purser and the surgeon offer two different versions of what happened when Billy died. The scientific surgeon is committed to objective truth, whereas the purser is more willing to see something extraordinary in Billy's death. It is unclear which interpretation of the event is true, and which is more of a rumor. Different witnesses remember an event differently. And that realization can be applied to the entire story told in Billy Budd (as this analysis has pointed out in previous chapters). Someone other than the narrator might have come to very different conclusions about what happened between Billy and Claggart than his narrator has done.
The purser continues to debate the issue with the surgeon, emphasizing the extraordinariness of Billy's stillness. The surgeon refuses to see the event as phenomenal, as the purser would have it, and tells the surgeon that will power is "a term not yet included in the lexicon of science."
The surgeon refuses to see Billy's stillness as one final outward appearance of his gentle inner nature, because he is committed to (or is he constrained by?) the rigid principles of science.