Why is unity sometimes regarded as the most important of all design principles?

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.  

what step of the art critique process do the following questions go with

apex. judge