This paper provides support for the unorthodox view that Hume’s simple ideas are most fruitfully understood as theoretical posits by showing that adopting this interpretation solves a lingering interpretive difficulty, the missing shade of blue. The missing shade of blue is thought to pose a serious challenge to the legitimacy of Hume’s copy principle. Thinking of Humean simple ideas as theoretical posits reveals a dialectical mismatch between Hume and his envisioned reader that, once understood, makes it clear that the case (...) holds little sway against the copy principle. The solution developed and defended has some significant advantages over extant solutions. (shrink)