Paine was a member of the radical dissident group around Johnson, also including Godwin, Wollstonecraft, Blake, Price, Priestley and Franklin (who encouraged his first visit to America). Priestley’s and Paine’s fortunes were intertwined, both being burned in effigy in England and ending as eminent yet half-forgotten refugees in America, former members of Jefferson’s intellectual circle. Paine left Godwin and others to see his ‘Rights of Man’ published while on Blake’s advice he fled to France. Condorcet was among his French ‘philosophe’ friends. Paine met Fulton in Paris, and gave a model of his iron bridge design to Peale.
His father James Mill was extremely and eccentrically ambitious for him. Jeremy Bentham was his godfather, George Bentham befriended him as a child in France, and Ricardo discussed political economy while out walking. Following a breakdown aged 20, he sought out Coleridge’s friendship (an important corrective), was awestruck on meeting Wordsworth, and found Southey very likeable. Comte became a long-term friend and influence. He was a close friend of Cole’s, worked under and then succeeded Peacock, corresponded with Babbage, Hooker, Leigh Hunt and Tocqueville, and unlike his friend Carlyle, abhorred slavery.
Moving to London, Mill met Bentham, becoming his close friend and enthusiastic supporter. He gave his son John Stuart Mill an extremely rigorous home education, dedicated to grooming him as his own and Bentham’s intellectual successor (not surprisingly, this hothousing led to the son’s mental breakdown). Mill was responsible for persuading his close friend and frequent visitor Ricardo to publish what became his most important work on economics. Dumont (like Ricardo) was another member of the circle around Bentham. Mill’s job at the East India Company, where he supervised Peacock, enabled him shamelessly to help his son.
Engels’ friend and collaborator Hess was responsible for his conversion to communism. He first met his great friend and collaborator, Marx, in Germany, but travelled to Paris to spend more time with him — 10 days that led to a lifetime’s work together, after Paris in Brussels, Köln and London (Engels, but not Marx, also lived in Manchester). In England, He often helped to support the frequently-destitute Marx. While he had many English acquaintances (even fox-hunting with fellow-businessmen), he made few friends. But he contacted Owen, whom he greatly admired, and wrote several articles for his newspaper.
Montesquieu contributed articles to Diderot’s Encyclopédie and was a close friend, though he avoided over-familiarity with Parisian circles. He visited Swift and Pope during a visit to England, and corresponded with Montagu. His good friend Helvétius tried to dissuade him from publishing some of his opinions, and kept quiet when the book became a public success. Montesquieu was a regular guest of d’Épinay.