Darwin has long been hailed as forefather to behavioural science, and even more so nowadays, with the growing popularity of evolutionary psychologies. This is the first book to examine Darwin’s own extensive writings about psychological matters. It finds that Darwin’s fulcrum was the agency of living creatures—both in his psychology and in his theory of evolution. A careful reading of Darwin’s writings on topics from climbing plants to babies shows that no individual-based theory of evolution can explain everything about human action. The interpersonal domain, group-life and culture, are also key, whether we consider the dynamics of conscience, emotional expressions or the dramas of desire. For example, Darwin argues that the anatomy and physiology of evolutionarily ‘purposeless’ facial movements gain meaning through their perception by others. His explanation of blushing adds a layer of complexity to such recognition—my blush results from my perception of how you are reading me. A similar reflexive dynamic governs how Darwin understands sexual desire, conscience, the setting of social standards, and the place of culture in human agency. Testing the main plank of Darwin’s psychology—that a capacity for group-interaction underpins the most human aspects of human agency—has awaited contemporary research, being recently confirmed by film-studies of young babies. Darwin’s writings frame a surprisingly well-resourced arena for elaboration of a socialized, agentic account of how we and our fellow creatures live. Moreover, Darwin stands at the forefront of moves toward an evolutionary biology in which organisms lead and genes follow.