According to the class personality quiz, that is:
Answer all 40 questions from the Arena quiz here: http://www.uesp.net/wiki/Arena:Character_Creation
Divide your answers by 4, then compare the numbers to the Morrowind result table here: http://www.uesp.net/wiki/Morrowind:Class_Quiz
I consistently get Witchhunter, probably because I'm so clever and I "think like a Witchhunter!"