What is the authors purpose in common sense

Common Sense (pamphlet) Common Sense is a pamphlet written by Thomas Paine in 1775–76 advocating independence from Great Britain to people in the Thirteen Colonies. 

To get down to the purpose though, Thomas Paine was telling the American colonists to rebel against the British monarchy and proclaim their independence. It was to encourage confused colonists to come and resolve into which side they should be on. These sides were the loyalists (Britain), and the rebels (Americans).