How should a free society protect privacy? Dramatic changes in national security law and surveillance, as well as technological changes from social media to smart cities mean that our ideas about privacy and its protection are being challenged like never before. In this interdisciplinary book, Chris Berg explores what classical liberal approaches to privacy can bring to current debates about surveillance, encryption and new financial technologies. Ultimately, he argues that the principles of classical liberalism – the rule of law, individual rights, property and entrepreneurial evolution – can help extend as well as critique contemporary philosophical theories of privacy.