Traditional Jews in the modern world generally try to reconcile their religious convictions with contemporary scientific findings, as in the case of interpreting Genesis in light of evolutionary theory. What happens when certain halakhot are based on biological assumptions which are no longer valid? Our instinct may be to assert that the law should change. Yet sometimes changing the law creates moral problems, forcing us to choose between scientific truths and ethical principles. We’ll explore three different examples of this problem and try to develop a framework for grappling with this dilemma.