Ian Keldon wrote:
She says "There is an old saying, or is it a myth, that Vulcans cannot lie...?"
Spock replies: "It is no myth..."
Technically speaking, he could make the case that he was saying: "It is not a myth that there is an old saying that 'Vulcans cannot lie'...", which would be literally true...just not answering her REAL question and letting her assume that he did.
Or, Spock could be saying that while it is not a myth that Vulcans cannot lie, there is in fact an old saying about Vulcan being incapable of lying.
Spock said nothing about the veracity of the old saying, one way or the other.