Our phones, our fitbits, our social media use, our internet searches, are all providing information about us. Information that can be used by commercial companies, by political parties, by governments. In the UK, there was a recent scandal when it was discovered that a company, Cambridge Analytica, had asked people to fill out a questionnaire, and used the results to tailor political messages to millions of Facebook users. Carissa Véliz is a philosopher at Oxford University and author of Privacy is Power. She argues that the harvesting of data is undermining liberal democracy.