Whether tracking prey, scoping a deal, scouting a romantic partner or raising our young, humans have always sought to deduce and then to influence the thinking of those about us. We often succeed, sometimes on a large scale: the results of such influence have included cults, theocracies and totalitarian propaganda, as well as populations responsive to benevolent peer pressure and the pro-social messages of nudge units. Most of us crave the approval of others and are therefore quite willing, whether we admit it or not, to allow their opinions to shape and inform our own.

At the same time, we value the right to be let alone – described by the American lawyers Samuel Warren and Louis Brandeis, in their seminal 1890 article ‘The Right to Privacy’, as the ‘most comprehensive of rights and the right most valued by civilized men’. A mental core impenetrable to others allows us to experiment with ideas, to dream, think and create in freedom. It enables, in the philosopher Thomas Nagel’s phrase, the ‘sheer chaotic, tropical luxuriance of the inner life’ to flourish.

The protection of that inner core is the subject of this engaging and thought-provoking book by the barrister and human rights expert Susie Alegre. Her two major themes are the unprecedented nature of the threat to our inner lives that is posed by modern digital technologies, and the need