The two authors study uncertainty and conviction in the light of the profoundly emotional nature of the analytical process. Following Melanie Klein, W. R. Bion develops the idea of oscillation between the paranoid-schizoid and depressive positions, an internal movement that is essential to psychic development. This pendular movement does not operate alone, but within a dynamic and complex relationship with the container-contained relationship and the analyst’s reverie. They go on to consider the link between negative capability and the “selected fact”, a prerequisite for interpretation. Interpretive conviction, acquired through the shaping of psychic materials, is always provisional. The analyst “without memory, desire or understanding” must develop the capacity to renounce the security and coherence of the depressive position in order to confront new fragmented and persecutory uncertainties, a necessary stage in psychic growth.