Psychoanalytic theorists have described primitive anxieties, including disintegrative fears about annihilation, identity loss, and the emergence of psychosis, as a foundation for borderline and psychotic mental states. These destabilizing anxieties occur across the dimensional spectrum of health and psychopathology. Openness to participatory countertransference involves both analyst and patient in primitive anxieties through their diminished psychic boundaries and their immersion in each other's internal world.