Interdisciplinary scholars, stressing the lack of firm disciplinary boundaries for British science in much of the nineteenth century, have pointed to evidence of mutual influence between the discourses of 'mental science', or psychology, and imaginative literature. This article treats Chapters on Mental Physiology (1852) by the English physician Henry Holland as a case study of heightened concern over the competing cultural authority implied by such mutual influence, and specifically over the inclusion of references to dramatic and lyrical works in early Victorian mental theory. It examines the medical author's self-conscious attempts to separate the developing profession of psychology from a tradition in philosophical discourse of enlisting imaginative writing for illustration and support. It further explores the way Holland strives to marginalise his text's occasional, paradoxical slips back into citing poetry by relegating this material to subordinate paratexts. How to safely deploy literature in service of science thus emerges as a key epistemological and rhetorical issue that Henry Holland, representing the consolidating field of British psychology at large, grapples with in his mid-century study of the mind.