Why were colonists against taxation without representation?

Colonists were against taxation without representation because they believed taxation required the consent of the people through their elected representatives, a principle they considered fundamental to English liberty since at least Magna Carta of 1215 and the English Bill of Rights of 1689. The argument unfolded on three levels.

The constitutional level held that Parliament had no rightful authority to tax colonists who could not vote for its members. Colonial assemblies had been raising their own taxes for more than a century by 1765, and most colonists held that those assemblies played the role for them that Parliament played for Englishmen at home. They distinguished sharply between trade duties accepted as a feature of empire and direct taxes imposed for revenue. Daniel Dulany of Maryland in his 1765 pamphlet Considerations on the Propriety of Imposing Taxes destroyed the British counterargument of virtual representation, the claim that members of Parliament represented all British subjects regardless of whether they could vote. He pointed out that even unrepresented English cities like Manchester and Birmingham shared geography and political access with neighboring boroughs that had members, while colonists were 3,000 miles away with no comparable lobby.

The political level held that taxation without consent reduced free citizens to dependents. James Otis told a Boston audience in 1761 during the writs of assistance case that taxation without representation was tyranny, a phrase that captured the colonial mood. Patrick Henry's Virginia Resolves of May 30, 1765 declared that any other body claiming to tax Virginians struck at British and American freedom alike and would tend to destroy the same. The Stamp Act Congress of October 1765 in New York City articulated the same principle in its Declaration of Rights and Grievances.

The economic level held that uncontrolled parliamentary taxation could ruin colonial economies and reward favored factions in London at colonial expense. Colonists feared that if Parliament could tax them at all, it could tax them as heavily as it pleased, divert revenue to support royal governors and judges who would then become independent of colonial legislatures, and ultimately establish a permanent system of imperial extraction. The Townshend Duties of 1767 confirmed those fears by explicitly using duty revenue to pay royal officials, breaking the colonial assemblies' control of the purse.

The deeper objection therefore was not the absolute amount of tax (which was modest) but the principle and the trajectory. If Parliament could tax property without consent, it could take any property, and that meant colonists held their liberty at the discretion of a distant legislature in which they had no voice.