was fundamental in introducing the ideas of "scientific socialism" into his own country, particularly through his 1874 work L’economia politica e la scienza, one of the earliest pieces of socialist theoretical writings in Italian.

Together with Carlo Cafiero, Errico Malatesta and Andrea Costa, he was instrumental in moving the Italian anarchist movement away from the collectivism it professed in the days of Mikhail Bakunin in order to adopt the communist formula "From each according to ability, to each according to need".

After a spell in prison, he left the country, moving to London first, where he launched and edited a magazine, "Redattori della Lotta!

He turned to more radical methods of propaganda by the deed in the 1880s and was forced to live on the run for several years, suffering a mental breakdown in 1884.

The commemorative plaque on Palazzo Covelli, the family home, in Trani bears his words: "I shall not sell myself either to any government or to any party...