This document summarizes Joe Brewer's argument for an emerging field called "culture design" aimed at intentionally guiding cultural evolution and social change. Brewer argues that humanity now faces unprecedented global risks that require new approaches to cultural change that integrate insights from complexity research, cognitive science, and cultural evolution. As an example, he discusses how culture design could help safeguard the critical Himalayan water supply on which billions depend by developing governance frameworks, understanding social dynamics, and guiding cultural change over multiple decades. Overall, the document makes the case that a grand synthesis is needed to integrate existing knowledge and practices from diverse fields in order to enable intentional social and cultural transformation at large scales.