Civil engineers evidence some discomfort in assisting in public policy decision making in a political arena. This paper is an effort to place the conflicts that emerge in this process in an historical perspective, and to provide professionals with assurances that their input can be effective if they understand the constraints on public policy decision making. Suggestions are made for improving effectiveness while also revealing that even the best professional analysis may be doomed to failure for reasons completely beyond the control of the planner. Finally, a case study presented to portray the impact of changing public values on professional recommendations will provide indications that circumstances beyond control may preclude final resolution of the conflict.