"As yet, I have not done anything to warrant Mr. Cranston's trust, though I intend to perform any tasks assigned to me to the utmost of my abilities." Spock was not given to false modesty, but he was cognizant of the fact that he would be required to earn any trust or respect given to him on this ship. He was starting from scratch, and while Captain Kirk's name might get him a leg up, it wouldn't help if he was found wanting.