Actual Causality

Actual Causality

By Joseph Y. Halpern

A new approach for defining causality and such related notions as degree of responsibility, degrees of blame, and causal explanation.
Hardcover $50.00 S £40.00
Paperback $37.00 S £29.00





A new approach for defining causality and such related notions as degree of responsibility, degrees of blame, and causal explanation.

Causality plays a central role in the way people structure the world; we constantly seek causal explanations for our observations. But what does it even mean that an event C “actually caused” event E? The problem of defining actual causation goes beyond mere philosophical speculation. For example, in many legal arguments, it is precisely what needs to be established in order to determine responsibility. The philosophy literature has been struggling with the problem of defining causality since Hume.

In this book, Joseph Halpern explores actual causality, and such related notions as degree of responsibility, degree of blame, and causal explanation. The goal is to arrive at a definition of causality that matches our natural language usage and is helpful, for example, to a jury deciding a legal case, a programmer looking for the line of code that cause some software to fail, or an economist trying to determine whether austerity caused a subsequent depression.

Halpern applies and expands an approach to causality that he and Judea Pearl developed, based on structural equations. He carefully formulates a definition of causality, and building on this, defines degree of responsibility, degree of blame, and causal explanation. He concludes by discussing how these ideas can be applied to such practical problems as accountability and program verification. Technical details are generally confined to the final section of each chapter and can be skipped by non-mathematical readers.


Out of Print ISBN: 9780262035026 240 pp. | 7 in x 9 in


$37.00 S | £29.00 ISBN: 9780262537131 240 pp. | 7 in x 9 in


  • How do we decide that someone is to blame for some misfortune, or that someone deserves credit for a favorable turn of events? Answering these questions and others depends on understanding how people represent and reason about the causal structure underlying specific events. The problem has plagued philosophers, legal and moral theorists, as well as psychologists. Recent years have seen enormous progress on this problem by using structural equations to model causal structure and defining causal relations in terms of counterfactuals. Much of this progress is due to the seminal work of Joe Halpern. His theories of blame and responsibility assignment and epistemic explanation are developed and expounded with full formal rigor in this seminal contribution.

    Steven Sloman

    Professor, Brown University, author of Causal Models: How People Think About the World and Its Alternatives and the forthcoming School of Thought: The Illusion of Knowledge and the Power of Collective Intelligence

  • What it might mean to say that some event was an 'actual cause' of some outcome—a conclusion that can be of crucial importance in deciding a legal case—is surprisingly difficult to characterize. This unique book describes the author's thoughtful quest to capture these subtleties in a formal language based on structural equations.

    Philip Dawid

    Emeritus Professor of Statistics, University of Cambridge

  • In this book, Joseph Halpern, a leading theorist of causality, develops a formal approach that revises and extends his earlier seminal work on counterfactual-based models for causation. The book includes a very informative, clear, and interesting discussion of the role and application of different features of causal models, and presents a new approach to modeling the causal features of responsibility, blame, and explanation. It is an important contribution to debates in philosophy and psychology about the nature of causal modeling and its application to real-world causation.

    L. A. Paul

    Eugene Falk Distinguished Professor of Philosophy, Department of Philosophy, University of North Carolina at Chapel Hill