Considerable historiographical controversy surrounds the question of why and how Copernicus decided to overturn the prevailing Earth-centered representation of the heavens. This essay summarizes some key elements of an explanation first laid out in The Copernican Question: Prognostication, Skepticism, and Celestial Order (2011) and subsequently expanded with further evidence in Copernicus and the Astrologers (2016). Copernicus’s defining problem situation is to be found in his involvement in a culture of astrological prognostication during his student days in Bologna (1496–1500). Just before (...) Copernicus’s arrival in the fall of 1496, Giovanni Pico della Mirandola’s attack on the foundations of astrology appeared from a prominent Bologna publisher. This publisher also produced several of the prognostications authored by Domenico Maria di Novara, in whose house Copernicus lodged. Among Pico’s many charges was a claim that astrologers do not agree on the order of the planets. Although the word “astrology” appears only once in Copernicus’s extant writings, it is certain that he was aware of Pico’s account of the astrologers’ disagreements on the matter of planetary order. The Copernican Question sets forth an inference about how and why Copernicus turned to heliocentrism that claims to be not only plausible but also the likeliest to correspond to what actually happened. (shrink)