Final answer:
The quote 'What's done is at an end' does not directly correlate with a specific historical figure or event in Tuscany's history, but it reflects the historical concept of the outcomes and interpretations of events, often related to the cyclic nature of history experienced by the Tuscans, particularly in Florence during the Renaissance.
Step-by-step explanation:
The phrase 'What's done is at an end', which purportedly sowed the seeds of evil for the Tuscans, does not seem to be directly traceable to a specific historical figure or event related to Tuscany directly in the references provided. It may be an allusion to a broader historical concept or narrative that relates to the cyclic nature of events, aftermaths, and the interpretation of history as seen through the eyes of victors or survivors. In the context of Florentine history, particularly during the times of the plague and ensuing conflicts with neighboring states such as Milan and Naples, as well as internal strife and perceptions of divine favor, one can draw parallels to the broader themes of hubris, downfall, and the moral interpretations of events as 'evil' or as divine retribution.
The theme of 'evil is the nature of mankind' and interpretations of events as 'evil designs' are common in historical and literary narratives, particularly during the Renaissance period when Florence was a hub of political and cultural change. The repeated good fortunes of Florence in avoiding conquest have been interpreted as a sign of divine favor, but the mindset this engendered could also be seen as the breeding ground for hubris and subsequent moral downfall.