This article introduces a significant yet largely overlooked problem in the law of torts: causal underdetermination. This problem occurs when the causal inquiry of a but-for test produces not one but two results, which are contradictory. According to the first, the negligent defendant is the likely cause of the plaintiff's injury, whereas according to the second, she is not. The article explains why causal underdetermination has escaped the radar of tort scholars and is perceived by courts as lack of causation. It demonstrates that the current practice in cases of causal underdetermination might lead to erroneous decisions, absolving negligent defendants of tort liability even when the evidence suggests that they are in fact the likely cause of the plaintiff's injury. This, in turn, the article asserts, may not only lead to underdeterrence among potential defendants, but also encourage manipulative litigation strategy to escape liability in retrospect. The article then proposes solutions that contend with causal underdetermination and resolve the difficulties that the current practice entails.

All observers of our legal system recognize that criminal statutes can be complex and obscure. But statutory obscurity often takes a particular form that most observers have overlooked: uncertainty about the identity of the wrong a statute aims to punish. It is not uncommon for parties to disagree about the identity of the underlying wrong even as they agree on the statute's elements. Hidden in plain sight, these unexamined disagreements underlie or exacerbate an assortment of familiar disputes—about venue, vagueness, and mens rea; about DUI and statutory rape; about hate crimes, child pornography, and counterterrorism laws; about proportionality in punishment; and about the proper ambit of the criminal law. Each of these disputes may hinge on deeper disagreements about the identity of the wrong a statute aims to punish, and these deeper disagreements can be surprisingly hard to resolve, fueled as they are by the complex inner structure of our penal laws and the discretionary mechanisms of their administration.

It is common to think that what theory of linguistic vagueness is correct has implications for debates in philosophy of law. I disagree. I argue that the implications of particular theories of vagueness on substantive issues of legal theory and practice are less far-reaching than often thought. I focus on four putative implications discussed in the literature concerning (i) the value of vagueness in the law, (ii) the possibility and value of legal indeterminacy, (iii) the possibility of the rule of law, and (iv) strong discretion. I conclude with some methodological remarks. Delineating questions about conventional meaning, legal content determination, and norms of legal interpretation and judicial practice can motivate clearer answers and a more refined understanding of the space of overall theories of vagueness, interpretation, and law.