This article considers the development of obsessional thinking in relation to the protective function provided by the early interpersonal environment. In particular, it explores the idea that the seed of obsessional thinking lies in the child's adaptation to and survival in an environment that either provides an overly strong shield against the world or one where the child is left highly exposed to the world. At the two extremes of shielding, where there is a less than or more than needed mediation of the external world, the child is at greater risk of developing a sense of an endangered relationship to the world. The main point here is that the malign omnipotence of obsessional thoughts grows within an environment whose capacity to balance exposing the child to the world and protecting him from that same world is skewed or where the child is unable to avail of the defensive shield as a means of safeguarding him from feelings of personal omnipotent destructiveness.