Design Science Research (DSR) has traditionally evaluated contributions by their effectiveness in solving specified problems within given contexts. While this problem-solving orientation and its focus on “fitness” have proven valuable, they provide limited guidance for assessing contributions whose primary impact lies in expanding the space of future design options. This paper introduces the concept of “fruitfulness” as a complementary evaluative dimension for DSR, defined as the capacity of design knowledge to expand or restructure the set of reachable future design states within a structured possibility space. Building on philosophical accounts of fruitfulness, insights from non-objective search in computer science, and possibility-centered views of science, this paper develops a conceptual model that distinguishes problem-specific fitness landscapes from a possibility lattice governed by prerequisite relations. It further differentiates artifact types by how they support problem-solving or option-making and illustrates fruitfulness through real-world and speculative examples. By reframing evaluation around what contributions make possible, the paper provides an epistemic foundation for anticipatory, speculative, and future-oriented design research.