His criticism of Napoleon III (Louis-Napoleon) and the Second Republic led to his imprisonment from 1849 to 1852; he later spent a period (1858–62) in exile in Belgium. His writings exercised considerable influence on the development of anarchism and socialism in Europe. He is chiefly remembered for his pamphlet What is Property? (1840), which argued that property, in the sense of the exploitation of one person’s labour by another, is theft. His theories were developed by his disciple Bakunin.