No other interval carries an equivalent ambivalence or affect. The major seventh simultaneously belongs to its tonic and nevertheless sounds a world apart. No other interval sounds so strange while belonging to its home major scale. For the other intervals, one must travel outside for a dissonant sound–Far from this crass and cartoonish dissonance, the major seventh uses dissonance to achieve transcendence. Or: the major seventh is beautiful by and through its very dissonance, through its long distance from tonic that is also the shortest distance possible.
(Chapter Four, Footnote 6)