 Although nothing seems freer than the power of thought, which isn’t “restrained within the limits of nature and reality” (EHU 2.4/18), Hume insists that our imagination is in fact “confined within very narrow limits”. We can separate and combine our ideas in new and even bizarre ways, imagining creatures we’ve never seen or faraway galaxies, but all the materials of thinking are ultimately derived from our impressions. Since “all our ideas or more feeble perceptions are copies of our impressions or more lively ones”; we are restricted to “compounding, transporting, augmenting, or diminishing the materials afforded us by the senses and experience” (EHU 2.5/19). 