In Common Sense, Thomas Paine argues for American independence. His argument begins with more general, theoretical reflections about government and religion, then progresses onto the specifics of the colonial situation.
Paine begins by distinguishing between government and society. Society, according to Paine, is everything constructive and good that people join together to accomplish. Government, on the other hand, is an institution whose sole purpose is to protect us from our own vices. Government has its origins in the evil of man and is therefore a necessary evil at best. Paine says that government's sole purpose is to protect life, liberty and property, and that a government should be judged solely on the basis of the extent to which it accomplishes this goal.
Paine then considers an imagined scenario in which a small group of people has been placed on an island, and cut off from the rest of society. In time, these people develop ties with one another, and lawmaking becomes inevitable. Paine says the people will be much happier if they are responsible for the creation of the laws that rule them. Paine is also implicitly arguing that such a system of representation is also better for the American colonists. Having expressed his disagreement with British reign in America, Paine proceeds to launch a general attack on the British system of government. Paine says the British system is too complex and rife with contradictions, and that the monarchy is granted far too much power. The British system pretends to offer a reasonable system of checks and balances, but in fact, it does not.
From here Paine moves on to discuss, in general, the notions of monarchy and hereditary succession. Man, Pain argues, was born into a state of equality, and the distinction that has arisen between king and subject is an unnatural one. At first, Paine says, the world was without kings, but the ancient Jews decided they wanted a king. This angered God, but he allowed them to have one. Paine presents pages of biblical evidence detailing God's wrath at the idea of the Jews having a king. The conclusion Paine reaches is that the practice of monarchy originates from sin, and is an institution that the Bible and God condemn. Paine calls hereditary succession an abominable practice. He says that even if people were to choose to have a king, that does not legitimize that King's child acting as a future ruler. Furthermore, hereditary succession has brought with it innumerable evils, such as incompetent kings, corruption, and civil war.
Having dispensed with the preliminary theoretical issues, Paine sets in to discuss the details of the American situation. In response to the argument that America has flourished under British rule, and therefore ought to stay under the king, Paine says that such an argument fails to realize that America has evolved and no longer needs Britain's help. Some say that Britain has protected America, and therefore deserves allegiance, but Paine responds that Britain has only watched over America in order to secure its own economic well-being. Paine adds that most recently, instead of watching over the colonies, the British have been attacking them, and are therefore undeserving of American loyalty.
Paine says that the colonies have little to gain from remaining attached to Britain. Commerce can be better conducted with the rest of Europe, but only after America becomes independent. Paine also asserts that if the colonies remain attached to Britain, the same problems that have arisen in the past will arise in the future. Paine argues that it is necessary to seek independence now, as to do otherwise would only briefly cover up problems that will surely reemerge.
Paine even proposes the form of government that the independent colonies should adopt. His recommendation is for a representative democracy that gives roughly equal weight to each of the colonies.
Paine explains why the current time is a good time to break free of Britain. Primarily, Paine focuses on the present size of the colonies, and on their current capabilities. He presents an inventory of the British Navy and gives calculations revealing how America could build a navy of comparable size. Paine recommends this as a way of ensuring America's security and prosperity in trade. Paine also argues that America is sufficiently small as to be united now. If time were to elapse, and the population of the colonies to grow, the same feeling of unity would not be present. Paine adds that if the Americans revolt now, they can use the vast expanses of uncharted land to the West in order to pay down some of the debt they will incur.
Paine says that as a colony of Britain, America lacks respectability on the international scene. They are seen simply as rebels, and cannot form substantial alliances with other nations. In order to prosper in the long term, the colonies need to be independent. Paine says that, by declaring independence, America will be able to ask for the help of other countries in its struggle for freedom. For all of these reasons, Paine says it is imperative and urgent that the colonies declare independence.