One of the most exciting debates in philosophy of imagination in recent years has been over the epistemic use of imagination where imagination epistemically contributes to justifying beliefs and acquiring knowledge. This paper defends “generationism about imagination” according to which imagination is a generative source, rather than a preservative source, of justification. In other words, imagination generates new justification above and beyond prior justification provided by other sources. After clarifying the generation/preservation distinction (Section 2), we present an argument for generationism (...) about imagination, which can be divided into two parts; the philosophical part and the empirical part. In the philosophical part of our argument (Section 3), we claim that generationism about imagination follows from what we call “INACCESSIBILITY”. According to INACCESSIBILITY, imagination is properly constrained by the imaginative constrainers (i.e., the prior representations that constrain the development of a scenario in imagination) to which non-imaginative belief-forming processes do not have access. In the empirical part of our argument (Section 4), we claim that INACCESSIBILITY is plausible in light of relevant studies and theories in the empirical literature, especially the literature on mental simulation (Section 4.1), core cognition (Section 4.2), and intuitive physics (Section 4.3). (shrink)