The most influential colonial response to the Townshend Acts was a series of twelve essays by John Dickinson entitled "Letters from a Farmer in Pennsylvania", which began appearing in December 1767. Eloquently articulating ideas already widely accepted in the colonies, Dickinson argued that there was no difference between "internal" and "external" taxes, and that any taxes imposed on the colonies by Parliament for the sake of raising a revenue were unconstitutional. Dickinson warned colonists not to concede to the taxes just because the rates were low, since this would set a dangerous precedent.