Born in Oneglia on the 16th of March 1741, in 1756 he became an Augustinian and, in order to complete his studies which were above all addressed to theology, modern humanistic studies and physics, he went to Pavia and Parma. In the latter he devoted himself to teaching, becoming a supporter of the reformist projects of Guglielmo Du Tillot (1711-1774), a refined man of culture who was active in Parma as the Minister of Finance from 1749 to 1771. In having become very powerful thanks to his position Tillot was the author of bold juridical reforms which, however, did not bear fruit due to the backwardness of the Duchy itself.
Amoretti's friendship with the powerful Minister earned him the hostility of the ecclesiastical authorities. Following Du Tillot's 'fall from grace' Amoretti was forced to move to Milan where he exercised the profession of preceptor. In Milan he was able to further advance his studies. He became an erudite Encyclopaedist and a very fecund polygraph, flanking his humanistic studies with an investigation of the nascent scientific culture.
His main interests were addressed to the agrarian sciences, geography and economics. In the light of this activity he took part in the reforms enacted by Empress Maria Theresa of Austria (1717-1780). A politically moderate man, he was removed from his official positions in Milan on the arrival of the French in 1796. Notwithstanding this setback, however, the following year he became librarian at the Biblioteca Ambrosiana, perhaps by way of a tepid demonstration of opposition to the new regime. In 1799, at the end of the Jacobin Triennial, Amoretti fully returned to the centre of Milanese political and cultural life.
He died in Milan on the 24th of March 1816.