Perhaps it is no accident that “Eureka” moments accompany some of humanity’s most important discoveries in science, medicine, and art. Ideas often appear unexpectedly in the human mind, so we must possess some capacity for appraising the idea in order to use it efficiently. Here we describe an account where the feeling of insight plays this adaptive role by signaling that a new idea appearing in consciousness can be trusted, given what one knows. Consistent with this perspective, recent experiments show that feelings of Aha tend to accompany correct solutions to problems. However, we have also shown that an artificially induced Aha moment can make false propositions seem true, demonstrating that Aha moments can exert influence regardless of ground truth. Drawing on these and other findings, we contend that humans use feelings of Aha heuristically in order to appraise new ideas that appear in awareness. In other words, from the manifold thoughts and ideas appearing in our stream of consciousness, the feeling of insight draws attention to the ‘best’ ones. Usually the heuristic works, but like all mental shortcuts, it is error prone. In this paper we encourage research on insight to move beyond questions about where insight comes from, and into questions about what insights do and how they affect decisions, belief, and the appraisal of ideas. It also brings to the forefront the dangers of false insight moments and their relevance for future research and the current age of information.