This study reviews allied literature and specific teacher educator behaviors that promote preservice teachers' development of a personalized, research-based elementary science teaching rationale (STR). Declaring absolutes is not the goal of the rationale. Rather, the goal is to initiate, among preservice teachers, the lifelong professional disposition of thoughtful teaching based upon cycles of reflection on one's experiences, the literature, and research on effective science teaching. The authors have found that the STR, as a key assignment in their methods courses, encourages these desirable "habits of mind."