What does it mean to be secure in the 21st century? Mark Beeson argues that some of the most influential ideas about national and even global security reflect untenable, anachronistic strategic views that are simply no longer appropriate for contemporary international circumstances. At a time when climate change poses an existential threat to the continuation of life itself, Beeson argues that there is an urgent need to rethink security priorities while we still can. Providing an explanation of the failures and dangers of the conventional wisdom, he outlines the case for a new approach that takes issues like environmental and human security seriously.