Defoe was an incredibly prolific writer, though many of his attributions are questionable. He was an ambitious businessman, but throughout his life he was continually plagued with money troubles (he went bankrupt for £17,000 in 1692; in 1706 he owed over £2000), and was often in prison for debt. He wrote many political essays and poems, preaching moderation and making commentary on government, politics, and economics. Some of these works caused him to be arrested for seditious libel, leading to further money problems. He also worked as a spy. His novels were very popular and evidently quite lucrative. His poem 'The true-born Englishman' went through over 50 editions. The DNB cites P. N. Furbank and W. R. Owens who explain that his enemies often condemned Defoe as a "mercenary hack."