Spock, the first officer whose advice was always effectual, possessed a strength of understanding, and coolness of judgement, which qualified him to be the counselor of the ship’s captain, and enabled him frequently to counteract, to the advantage of them all, that eagerness of mind in Captain Kirk which must generally have lead to imprudence. Spock had an excellent heart, positioned somewhere near his kidneys; his feelings were strong, but he knew how to govern them: it was a knowledge which his captain had yet to learn, and which one of his fellow crew members had resolved never to learn.
Dr. Leonard McCoy’s abilities were, in many respects, equal to Spock’s. He was sensible and clever; but eager in every thing; his sorrows, his joys, could have no moderation. He was generous, amiably cynical, interesting: he was everything but logical.