If You Can Do More, Teach
While Kirk undergoes the most profound change of all the characters in the film, his redoubtable first officer Spock remains the same as he always was: wise, astute, courageous and loyal unto death.
Oh, jeez. Now we're crying. You were supposed to live long and prosper, Spock. You were supposed to live long.
As a Vulcan, Spock's given himself over to the tenets of logic, but that logic is tinged with a deep and abiding compassion for all living things. That one-two punch lets Spock save the ship in ways that Kirk never could.
It also makes him an awesome teacher. When Kirk became an Admiral, Spock became Captain of the Enterprise. As the film opens, he's using his position to train a new crew: he's acting as mentor, not unlike Gandalf in The Lord of the Rings or Dumbledore in Harry Potter. He's there to pass on his hard-earned wisdom to his trainee crew, and hopefully get them up to speed as the next generation of galaxy-savers.
Seriously. Where was Spock when we needed mentorship?
KIRK: I told Starfleet all we had was a boatload of children but ...we're the only ship in the Quadrant. Spock, these cadets of yours, how good are they? How will they respond under real pressure?
SPOCK: As with all living things, each according to his gifts.
And his sage-like instruction doesn't stop with his students. He's just as much of a teacher to his old friend Admiral Kirk. The lessons he teaches are harder, of course—he dies while teaching 'em—but Kirk needs to hear them just as badly.
SPOCK: I never took the Kobayahsi Maru test until now…what do you think of my solution?
By sacrificing himself to save the ship, Spock demonstrates how to face certain death, and the true meaning of selfless leadership.
Even if you weren't familiar with Trek before seeing Star Trek II, you can sense how much of a loss Spock's death is to Kirk… and why Spock's at peace with his decision. After all, he's dying in the defense of logic—his guiding philosophical tenet—as well as saving his entire crew.
SPOCK: Don't grieve, Admiral...it is logical. The needs of the many...outweigh…
KIRK: ...the needs of the few.
SPOCK: Or the one.
Hard to argue with his wisdom…or complain about the way he goes out. By facing death the same logical way he faced life, he leaves peace and wisdom alive and well behind him.