This article proposes a novel theory of the truth of doctrine. A signpost theory of the truth of doctrine is informed by practice-based philosophy of science. I argue that a theory of the truth of doctrine needs to explain the construction, use, and judgement of doctrine. So, I raise questions about the truth of doctrine in reference to the relation between a theory of the truth of doctrine and the role of doctrine in the religious practice of believers. I argue that a signpost theory of the truth of doctrine learns from an empirical understanding of measurement and modelling in scientific practice. The examples of entropy and time provide insights into the construction, use, and judgement of measurements and modelling in scientific practice. An empirical understanding of measurement in scientific practice provides resources for linking representations with reality without ignoring the contextual construction, use, and judgement of representations. I conclude with a brief articulation of how a signpost theory of the truth of doctrine learns from an empirical understanding of measurements and models in scientific practice by highlighting the similarities and differences between the construction, use, and judgement of doctrine and of scientific representations.