Final answer:
John Dickinson argued that Parliament's taxation of the colonists without their representation was unconstitutional, tying it to the notion of no taxation without representation. He differentiated between legitimate regulation of trade and illegitimate direct taxation for revenue, underscoring colonists' demands for direct representation.
Step-by-step explanation:
John Dickinson, a colonial American lawyer and politician, argued that it was unconstitutional for Parliament to tax the colonists because they were not represented in Parliament. In his 'Letters from a Pennsylvania Farmer', Dickinson insisted that taxes imposed without the consent of the colonies, which had no direct representatives in Parliament, were a violation of their rights as English subjects. Dickinson, along with other colonists, believed it was permissible for Parliament to impose taxes to regulate trade as part of its authority over the Empire, but not to raise revenues directly from the colonies. This belief stemmed from the principle of no taxation without representation, rooted in British constitutional law, which emphasized that only the colonial legislatures or direct representatives of the colonists had the authority to levy taxes on them. The Stamp Act and other revenue-related acts were seen as an attempt by Parliament to extend its powers beyond what was constitutionally acceptable, which ultimately contributed to the resistance that led to the American Revolution.