Galileo as a Commentator on Almagest I.3

The fourth chapter focuses on Galileo’s critique of the traditional interpretation of Ptolemy’s theory on why stars appear larger at the horizon, as hinted in Alm. I.3. Galileo’s theory, also seen in The Assayer (1623) and Alimberto Mauri’s Considerations (1606), is similar but not identical to the one found in Theon’s commentary. Although it is unclear if Theon was a direct source, the chapter shows Galileo critically engaging with the Almagest and challenging conventional views.