The visit puts a focus on the plight of workers whose lives have been made precarious by years of economic crisis, including in Italy where a high jobless rate, especially among young adults, drives many to leave the country.
Speaking to some 3,500 industrial workers, many in factory uniforms or hard hats, Francis distinguished between good entrepreneurs, who "share the labours of workers and share the joys of work" to create something together, and speculators who are not bothered when they fire workers in a search for profit.
"The speculator doesn't love his business, doesn't love the workers, but only sees the business and workers as a means to make profits."
He also denounced those who claim that workers do their jobs only for the money, saying that this assumption "denies the dignity of work."
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Francis, an Argentine whose parents left Italy in the early 20th century, also referred to his personal feelings aroused by visiting the port city, the departure point in the past for Italians seeking new lives in North and South America.
After the visit at the factory, Francis met with bishops, priests and nuns at the Cathedral of San Lorenzo.
Later the pontiff also planned to meet with poor and homeless people as well as refugees and prisoners.