The article analyzes the question of the retroactive effect of judicial decisions. It surveys the history of retroactivity doctrine to demonstrate that the current approach to retroactivity jurisprudence is a consequence of the Warren Court's adoption of the principle that parties should be governed by the law in effect at the time of their actions. This principle leads to a theoretical framework that suffers from serious difficulties. In particular, it is unable to distinguish between cases presented on direct and collateral review, and consequently unable to reach a satisfactory treatment of habeas petitions based on changes in law. The article recommends a return to the earlier jurisprudence under which courts decided cases based on the best current understanding of the law, and demonstrates that this approach provides a sound basis for retroactivity.