We're used to thinking that big ideas are dreamed up on land by philosophers and writers anchored to their desks.

In his new book, Outlaws of the Atlantic: Sailors, Pirates, and Motley Crews in the Age of Sail, Marcus Rediker, distinguished professor of Atlantic history at the University of Pittsburgh, turns that assumption upside down, showing that many of the ideas that shaped the modern world were, in fact, born on the ocean waves among sailors, pirates, and slaves.

Here he explains how Johnny Depp got it wrong, why Horatio Nelson can be regarded as a "maritime criminal," and how a motley crew in Boston inspired Samuel Adams to coin one of the defining phrases of the Declaration of Independence.

You say that we've been looking at history "through the wrong end of the spyglass." What do you mean by that?

I mean that we have concentrated on the glories of the great national heroes and neglected the people whose labor made them possible. If we want to understand how the world was connected, how the continents became part of the planet in an interactive way, we must understand the ships and the sailors who made those links.

Concentrating on Captain Cook and Nelson can get us only so far. We need to understand the ordinary people who made history at sea. Hugely important modern ideas about race and class were born at sea. But we tend to think that history happens on land and regard the sea as a kind of historical void. This blinds us to important aspects of the world historical process. It's what I call the "terracentric" vision.

You call the European man-of-war a laboratory of radical social ideas.

Large northern European seagoing vessels, which emerge in the 16th and 17th centuries, become by the 18th century the most important technology in the world. They can be seen as a precursor of the factory, in the sense that they required large numbers of wage workers to come together and operate machinery to make the vessel go.

That's a work process that creates value, tremendous value, for the world economy. But when workers are organized to sail these ships for merchants, or kings and queens, their organized cooperation also led them to imagine new projects of their own.

They start to think about their own lives and cooperate for ends other than the ones they were brought together to serve. One of the best examples of this is in the origins of the term "to strike." Most people don't know that the strike originates at sea, in the port of London, in 1768, amidst a wage cut. So sailors went from ship to ship and took down the sails—which is called "to strike the sails."

You go so far as to suggest that the seeds of the American Revolution were sown not on land but at sea. How so?

One of the origins of the American Revolution lies among sailors and their resistance to impressment. The [British] Royal Navy was chronically undermanned; wages were poor, so the navy resorted to impressment in order to find labor.

Sailors, especially in North America and the West Indies, began fairly early in the 18th century to fight back against this practice. And by the 1760s the battles between sailors—in ports like Boston, New York, or Philadelphia—and the Royal Navy had reached a kind of fever pitch. They say they're fighting against tyranny, because ship captains were often tyrants, in the name of their liberty. That's a literal definition of liberty, because when sailors were on shore they were "on liberty."

Sailors essentially take direct action. They form mobs. They try to capture men back from the press-gang. Or seize the ship's boat, carry it to a public place, and set it on fire to dramatize their resistance.

So, sailors are providing an example of the way in which American colonists should all fight back on behalf of their liberty against tyranny. These sailors' riots then influence important figures like Sam Adams in Boston, who watches a motley crew battling the press-gang and articulates an idea which will become the basis of the Declaration of Independence: that all men are created equal.

View Images The book debunks the standard image of the pirate—a man with a patch over one eye, a hook for a hand, and a peg leg. Photograph courtesy of Beacon Press

One of your favorite characters is an escaped slave called Caesar. Tell us about him.

Caesar represents a perfect example of the will to be free. One of the themes in this book is that even when placed in extremely oppressive circumstances, people will find creative ways to resist.

Caesar was an enslaved African. That's the only name we have for him. He first shows up in the historical record in 1759. He had been working as a slave on the waterfront and escaped by sea. He appears again in the record ten years later, where he has once again taken off. Apparently, he was recaptured the first time and probably sold by his owner. He ends up again working on the waterfront. He has the skills and knowledge of a sailor and he has connections. So, he manages to get away again.

And for a second time an owner runs an advertisement in the paper to try and track him down. This reveals a singular fact about Caesar: He had no legs. So here was a man, who was a runaway, who actually had no legs but still managed to use his intelligence and the will to be free to find a way to escape slavery twice.

Say the word "pirates," and most people think of Johnny Depp and Keith Richards hamming it up in Pirates of the Caribbean. It wasn't quite like that, was it?

[Laughs] The Hollywood stereotypes of pirates have been very successful. But they don't really recover the rich history of who these outlaws were. If you go back to the original sources, thousands of pages of court cases and depositions and newspaper articles, you find that there was a much more complex story to be told about the origins of the golden age of piracy, in the 18th century.

The traditional story is that pirates were brutes and criminals driven solely by greed. These things have an element of truth, as all stereotypes do. But what I found is that most pirates were just common sailors, many of whom had been brutalized in the merchant and naval ships of the day. So they started capturing vessels and setting up their own ships so they could live a better life, even if for a short while, because a pirate couldn't be expected to live very long.

What was fascinating to me was the extraordinarily different way in which they organized their ships. They were coming from utter autocracy, where the captain had complete power over the crew, even the power to whip someone to death.

But when the mutineers took over a ship, the first thing they did was to elect their own captain. They practiced democracy. They also divided up the loot, the booty, in an egalitarian way. Pirates even created a kind of social security system, to provide for their fellow pirates who were injured in battles.

So what I've attempted to do is take that standard stereotype of the pirate—a man with a patch over one eye, a hook for a hand, and a peg leg—and relate that back to the original conditions of the sailors' life.

A lot of people will be upset, particularly in Britain, to see Horatio Nelson, a captain adored by his crews, branded as a "maritime criminal."

[Sighs] I knew this would upset people. But I felt like it was a point that was useful. It's actually a quotation from Jamaica Kincaid, the novelist, who said that in her native Antigua, a lot of the streets are named for what she calls "maritime criminals" like Nelson.

What I wanted to show in quoting her is that those people we regard as heroes and those people we regard as criminals is relative to your point of view. In my book, the outlaws loom large. This is, in a sense, the maritime world turned upside down. I've not done research on Nelson, so I don't have anything specific to say about him. But insofar as he represents an older-fashioned kind of maritime history, I'm posing an alternative.

There's a new piracy problem today, in Somalia, which was the subject of another Hollywood movie, Captain Phillips. Are there parallels with the pirates you portray?

I try to understand the circumstances of sailors in the 18th century and the choices they made. I emphasize that they were trapped in an extremely violent system, and that their own violence as pirates was a response to that.

I think a similar approach would help us to understand piracy in Somalia. Piracy dates back to ancient Greece. Anytime vessels with lucrative cargo passed through areas of poor people who also had vessels, they frequently attack the larger ships and try to capture them.

What strikes me as important about Somalia is that many of the pirates come from destroyed fishing communities. European and Japanese fishing fleets had overfished the waters around Somalia and destroyed the livelihoods of a lot of the fishermen. So they turned to piracy in response.

In that sense, I think there are some similarities between the old piracy and the new. These are the responses of poor people, who don't have a lot of other choices. There are political and economic issues. And global inequality is certainly one of them.