The mechanical and reductive ideals of much of modern science leave it ill-equipped to recognize, let alone account for, the agency of animals. So says a tradition of criticism well represented in the writings of the British behavioural biologist W.H. Thorpe FRS (1902–1986). This paper recovers the range of overlapping debates and developments, philosophical and religious as well as scientific, which led Thorpe to champion animal agency in the period and place much better known now as headquarters for the neo-Darwinian Modern Synthesis. A retracing of Thorpe's path through such forgotten domains as applied-science Lamarckism and the philosophical psychology of Leonard Hobhouse complicates a now-standard picture (which Thorpe himself promoted) of the Modern Synthesis as inimical to animal agency. Largely thanks to Thorpe's work, as publicized by Julian Huxley, the Modern Synthesis revitalized the fortunes of what became one of the mainstays of agential science, the Baldwin effect.