The present volume draws together original and significant essays from a number of leading authorities which identify areas of the modern criminal law where there are significant conceptual difficulties. The project developed from a series of seminars in Cambridge University, in which leading Anglo-American philosophers, criminal lawyers and legal theorists explored subjects such as attempts, intention, justification, excuses, coercion, complicity, drug-dealing and criminal harm. The topics covered in this impressive collection were chosen for their topicality as well as their theoretical and practical significance.