In part one of Rights of Man, Paine is primarily concerned with providing a rebuttal to Edmund Burke's Reflections on the Revolution in France. In his pamphlet, published in 1790, Burke is harshly critical of the French Revolution even in its earliest stages, before it begins to turn violent. Paine forcefully answers Burke's charges, claims that Burke doesn't know what he's talking about, and claims that the British system of government is destructive of human rights and needs to be changed.
Like other progressives, Paine was taken aback by Burke's attack on the French Revolution, partly because Burke had been sympathetic to the American colonists when the American Revolution began 15 years earlier. Paine heavily criticizes Burke's apparent belief that the English had deliberately renounced the right to choose their own form of government in the declaration of loyalty Parliament had made to King William and Queen Mary a century earlier. In part one of Rights of Man, Paine is concerned both with pointing out the positive qualities of the changes made in France since the Bastille was stormed and with arguing that other countries, including (or especially) Great Britain, should make the same kinds of changes, such as eliminating the monarchical system and establishing a constitutional democracy (which he denies exists in Britain at the time). He then quotes the French National Assembly's Declaration of the Rights of Man and the Citizen as a statement of the human rights which should be safeguarded by the ideal government.
Perhaps the central point of Paine's treatise, however, is his debunking of the idea that the English Constitution is a reality. Paine, in opposition to Burke and most English or British experts, goes so far as to deny that the English Constitution even exists, because it is not a discrete written document produced in one place and time, as the US and French constitutions are.
Paine was considered a radical thinker in his time. After his service to the American cause from 1775 to 1783, he returned to Europe and attempted to spread revolutionary principles to his native England. Rights of Man was the focal point of his efforts in this regard.