In the context of international debates about teachers' knowledge, this essay reports a study of how and why a cohort of English trainee teachers of Religious Education used their personal life knowledge in their teaching. Four possible reasons for their commitment to this practice are examined. A belief in the value of openness, a desire to motivate and engage their pupils, and a need to create "bridges" between the pupils' worlds and those of religions are considered. The possibility that trainees used their life knowledge to bridge a "gap" between their personal and professional lives is also discussed. The findings of Communication and Teacher Effectiveness research are used to indicate the potential benefits of the practice and the works by Aldenmyr and Furedi are drawn upon to highlight potential dangers. The author concludes that the sharing of teachers' life knowledge can benefit pupils, but that teachers need to reflect on the dangers and further research is needed to support this.