The Jesuit astronomers who had celebrated Galileo’s telescopic discoveries during his visit to Rome in 1611 now felt estranged by the biting satire of the The Assayer. The controversy concluded with this final reply. Both comets and cosmic systems remained enigmas. If mathematical methods and the evidence available at the time could not disprove the Tychonic system, then Galileo faced the daunting prospect that scientific knowledge might be provisional, with certainty an elusive goal, even in mathematics.