This chapter discusses measures undertaken by early modern states to evaluate potential impostors to provide new reading of the ploys of the Sidereus Nuncius. In the debate over the nature of sunspots, Sagredo wrote an aggressive letter to Markus Welser, threatening to unmask Galileo’s pseudonymous opponent, ‘Apelles.’ Sagredo claimed that Apelles’s astronomical observations were invalid because of his politically compromised identity as a Jesuit. He charged Apelles with the same anti-Venetian sentiments exhibited in the recent scandalous book Squitinio (1612). By analysing both other scientific publications of the period, such as Galileo’s The Assayer (1623), and contemporary writings on pseudonymity, the ahistoricity of our assumptions of ‘normal’ scientific authorship are exposed. In their place, it is proposed that historians of science immerse themselves more deeply in their periods’ general cultural practices, to restore science to its more meaningful place as a socially produced form of knowledge.
Keywords: impostors, sunspots, Markus Welser, Christoph Scheiner, Squitinio, The Assayer, pseudonymity