This paper considers the discoveries that have appreciably changed our understanding of the physics of solar flares. I identify a total of 42 discoveries from all disciplines, ranging from Galileo's initial observation of faculae to the recent discovery of strong limb brightening in 10-MeV γ-radiation. The rate of discovery increased dramatically over the past four decades as new observational tools became available. My assessment of significance suggests that recent discoveries - though more numerous - are individually less significant; perhaps this is because the minor early discoveries tend to be taken for granted. In spite of the many facets of flare physics that have been explained or at least well-described, many fundamental questions remain unresolved.