The disposition to do this is encouraged by the monistic tendency, which everywhere and always looks for a unique principle. Monism, in so far as it is a universal psychological tendency, is a characteristic peculiarity of the manner of feeling and think
Jung identifies monism as a pan-human psychological disposition to seek a single governing principle, diagnosing it as the root error that permits either the collective or individual pole of the psyche to exclude the other.
, Two Essays on Analytical Psychology, 1953thesis