"' Praise God' is the title of this letter. For when human beings claim to take God's place, they become their own worst enemies." In Laudato Si', his historic encyclical of 2015, Pope Francis firmly established ecological concerns as central to the agenda of Catholic Social Teaching. Along with a spiritual framework on care for creation, he outlined such issues as climate change, biodiversity, and the peril facing our oceans, and offered a comprehensive guide to integral ecology. Now, comes a shorter but even more urgent call: Laudate Deum, which focuses specifically on the climate crisis. As Erin Lothes Biviano writes in her introduction, Pope Francis here writes as a prophet, priest, poet, and most of all "a pastor, deeply concerned for people throughout the world, and above all for the poor." Disappointed that not enough has been done in the intervening years, Francis addresses the irreversible effects of increasing global temperatures, the decrease in ice sheets, and other signs of the times. He critiques the "technocratic paradigm," the ongoing addiction to a fossil-fuel economy, and the "weaknesses of international politics," while leveling particular criticism at those who sow resistance and confusion. With selections in this edition from Laudato Si' that focus on pastoral, theological, and spiritual themes, Laudate Deum is a call to face the preeminent crisis of our times and to draw on all our spiritual wisdom, scientific knowledge, and political will to meet the challenge.