The Mansfieldian Moment

"Rule Britannia, rule the waves," went the popular song of 1740. "Britons never will be slaves." Written at a moment when Britain was at war on the seas, battling for trade and for colonies, the song identified ordinary British people with a broader empire. Freedom came with rule overseas. Freedom and rule, together, exemplified the opposite of human bondage, for those who sang the song. Freedom explained itself: the opposite of slavery. Rule explained the enslavement of others in the empire.

There is not much evidence that this song was particularly beloved in British North America. Its invocation of slavery may have been a bit too overt, with slaves so nearby. Certainly the emphasis on British overseas rule clashed with colonial presumptions of self-government. During the early eighteenth century the growth of the empire and the growth of slavery posed fundamental questions about freedom, governance, and national identity. The unwritten British constitution, composed of Parliament's laws and judges' interpretations, proved flexible enough to handle these questions until an expensive world war and a vast addition of North American territory raised them anew. The politics of slavery played a significant part in that imperial crisis and in its better-known results: a revolutionary war and the creation of the United States.

In the early modern world, the British came late to empire, and still later to slavery. The Spanish had pioneered both institutions, and the British did not so much decide to enslave natives in the Americas or Africa as they found ways to get in on the system. Early idealism, whereby Englishmen imagined they would find more peaceful ways to exploit the New World's resources and compete with the rest of Europe for the balance of power on the Continent, gave way to battles for conquests and similar strategies. Rather than being between slavery and freedom, the basic difference lay between the gold-mining operations of the Spanish Empire and the agricultural model of the English, who at first had to settle for lands without precious metals. When the English gained footholds and then settled in zones like Barbados that supported cash crops like tobacco and sugar, they turned first to native laborers, then to their own poor populations, and finally to Africans in growing numbers. During the mid-to late seventeenth century, the mainland colonies of Virginia and, later, South Carolina grew rapidly on the Caribbean model. Within a few decades, the northern colonies of New England, Pennsylvania, and New York experienced their own population explosions, thanks to the opportunities to supply the southerly tobacco and sugar colonies with food, with ships, with all kinds of supplies. During the same years, more and more Africans toiled in those places.

Each colony was different — in size, in trade, in form of government, and in labor supply. Slavery was one of the institutions that exemplified these differences. Yet during the eighteenth century each prospering colony became more enmeshed in an imperial system of supply and demand operating within a competitive world often at war. The more integrated into the Atlantic system each colony became, the more slaves arrived there, on the same ships that delivered New World produce and returned Old World supplies in exchange.

Theoretically, the British Empire ran its colonies and their economies for the benefit of the mother country and, secondarily, the empire as a whole. In practice, this meant considerable autonomy for the colonists, and allowances for local customs by imperial officials. According to the folks whose parents had migrated across the ocean from various parts of the British Isles, these very freedoms were what made them English. A series of crises in late-seventeenth-century England had helped develop distinctly English ideas of traditional liberties, guarded by Parliament and a king who no longer was divinely authorized but rather was himself a guardian of parliamentary liberties. Originally, the king had been the special overseer of overseas "dominions" and used them as favors, giving away lands and trading well-paying jobs like colonial governorships for political support in Parliament. Eventually, the king ruled his dominions in consultation and cooperation with Parliament through the Board of Trade, which had the power to disallow the acts of the provincial assemblies or legislatures. The two revolutions in late-seventeenth-century England — the civil wars of 1641 to 1660 and the "glorious" overthrow of James II in 1688 — tended to strengthen the parliamentary central government of England while drawing attention away from the colonies. Colonists used the opportunity to claim their own liberties and identify those claims with constitutional developments in England.

What no one wanted to face was that the claims of Parliament to extend its rule in the name of the British people could conflict with the claims of white colonists to run their own local societies in the name of their "English" rights. Occasionally, when the interests of the home country conflicted with those of some colonial leaders, a standoff occurred. Sometimes colonial officials would back down, or find a compromise. Sometimes they would decree otherwise — compelling obedience to central authority. Sometimes colonists would simply disobey, trusting distance to cover the difference between the letter of the law and its lax enforcement. British imperial government, and the fighting of its increasingly regular wars with the French and Spanish empires, was a matter of constant negotiations, and, increasingly, lobbying as well. The mainland colonies began to send informal representatives to London, as well as letters "home" on the same ships that carried their goods to distant markets.

Because of the sheer centrality of slavery in the British Empire by the mid-eighteenth century, some of the more difficult to resolve controversies between individual colonies and the home government did concern slaves and the things slaves produced. Northern mainland colonists expressed great frustration, for example, when Parliament passed the Molasses Act of 1733. This law tried to make it more difficult for British American shippers and rum distillers to trade with the French sugar-producing colonies — a trade that hurt the British West Indies. That such legislation passed Parliament showed how much more important the sugar colonies, with their highest proportion of slaves to settlers, seemed to London. The experience of losing out to the British West Indians did not cost Rhode Island and Massachusetts merchants much trade. Instead, it led them to become bolder smugglers. In Rhode Island, where governors were elected, they also learned to support men like Stephen Hopkins, who made it unofficial policy to discourage the collection of duties and the capture of illegal traders.

Colonists began to develop arguments for why freer trade, and customary liberties, suited the empire as well as the...