In their criticisms of authoritarian politics, British modernists of the interwar years often drew on a physiological discourse of conditioned reflex, one popularized by Ivan Pavlov’s lectures, Conditioned Reflexes (1924, trans 1927). For writers like Huxley and Woolf (as well as post-war writers like Arendt), fascism represented a creeping and pernicious form of organizing political modernity according to automatic, habitual, or reflexive behaviors, rather than according to the rational agency of individuals. Like Woolf’s Three Guineas, Rebecca West’s Black Lamb and Grey Falcon offers a critical analysis of fascism that stresses its dependence on those political reflexes enforced by “atmosphere.” Yet, this article suggests that West also appropriated Pavlovian ideas of reflex in order to articulate her own, positive sense of national identity in Black Lamb. The epic form of this text reflects West’s affirmation of national identities grounded in collective reflexes and the materially conditioning work of atmosphere.