Letters from a Farmer in Pennsylvania is a series of essays written by the Pennsylvania lawyer and legislator John Dickinson (1732–1808) and published under the name "A Farmer" from 1767 to 1768. The twelve letters were widely read and reprinted throughout the thirteen colonies and were important in uniting the colonists against the Townshend Acts. The success of his letters earned Dickinson considerable fame. 
While acknowledging the power of Parliament in matters concerning the whole British Empire, Dickinson argued that the colonies were sovereign in their internal affairs. He thus argued that taxes laid upon the colonies by Parliament for the purpose of raising revenue, rather than regulating trade, were unconstitutional.
In his letters, Dickinson foresees the possibility of future conflict between the colonies and Great Britain, but cautions against the use of violence until "the people are fully convinced":
If at length it becomes undoubted that an inveterate resolution is formed to annihilate the liberties of the governed, the English history affords frequent examples of resistance by force. What particular circumstances will in any future case justify such resistance can never be ascertained till they happen. Perhaps it may be allowable to say generally, that it never can be justifiable until the people are fully convinced that any further submission will be destructive to their happiness.— Letter III
According to Mel Bradford, "The manner of Dickinson’s twelve letters is well suited to their matter. In form they belong to the 'high' or 'sober' tradition of English political pamphleteering — as does Common Sense to its 'rough and ready' but popular counterpart."  Bradford argued that the letters had antecedents in the writings of " Milton, Swift, Addison, and Burke," as well as the authors of Cato's Letters and the Roman statesman Cicero.