Inasmuch as a man is merely collective, he can be changed by suggestion to the point of becoming—or seeming to become—different from what he was before. But inasmuch as he is an individual he can only become what he is and always was.
Jung distinguishes authentic individuation-driven change from suggestive conformity, arguing that genuine personality change fulfils rather than replaces the individual’s essential nature.
, The Practice of Psychotherapy: Essays on the Psychology of the Transference and Other Subjects, 1954thesis