The Dictates of Poetics

From Memory Alpha, the free Star Trek reference.

The Dictates of Poetics is a book by Vulcan writer T'Hain, in which T'Hain wrote:

"A character's actions must flow inexorably from his or her established traits."

Tuvok quoted this line while writing a holonovel with Tom Paris in 2373. (VOY: "Worst Case Scenario")