Matthiessen was one of many educated men and women across who reacted with enthusiasm to the outbreak of the revolution in Paris in 1789. In July 1790 he was one of approximately eighty leading Hamburg intellectuals who took part in the "Revolution Festival" arranged by Sieveking and held in a pub garden at Harvestehude to celebrate the first anniversary of the Storming of the Bastille. During the winter of 1790/91 he stayed in Paris, becoming a member of "Club 87" and established a connection with de La Rochefoucauld. By July 1791 he was back in Hamburg where he was elected to membership of the "Kollegium der Armenanstalt", overseeing Caspar Voght's . Later his trips to Paris became increasingly frequent, and he made it a personal priority to provide support for Parisians in need. During his final years he was providing support for eighty families, visiting them all for as long as his strength permitted it.