The Grid, an instrument devised to help the analyst record and elaborate observations arising from the analytic encounter, demonstrates how mathematics can be applied to locate the development, evolution and transformation of psychic elements and events. Caesura takes its title from Freud's observation: "There is much more continuity between intra-uterine life than the impressive caesura of the act of birth would have us believe". Here Bion speculates on the relationship between physiological and psychological birth, and the possibility that a pre-natal "primitive sensitiveness" may carry over and inform later psychological life.