In Galileo’s Dialogue, Simplicio presents traditional Aristotelian arguments.
The 1632 book stages a four-day conversation about the Ptolemaic and Copernican models of the cosmos. Simplicio is the committed follower of Aristotle and Ptolemy, while Salviati argues for the Copernican position and Sagredo acts as an intelligent, initially more neutral participant.
Simplicio’s name recalls Simplicius of Cilicia, a sixth-century commentator on Aristotle. Galileo’s readers also noticed a possible wordplay: semplice means “simple” in Italian, which made the character seem foolish or overly dependent on authority. Galileo may have based aspects of him on conservative contemporary philosophers, although the character is not simply a historical portrait.
A common mix-up is to identify Salviati as the Aristotelian speaker because he discusses Aristotle so extensively. In fact, Salviati usually examines and rebuts Aristotelian claims, including the idea that the heavens are perfect and unchanging. The Dialogue was formally presented as a balanced comparison, but its arguments strongly favor the moving Earth and the Copernican system.