The quest for the Northwest Passage was based on philosophy, not evidence

The HMS Terror, pictured here in an 1838 painting by William Henry Smyth, was trapped in pack ice west of Baffin Island and stranded on an ice floe for 118 days during an arctic voyage, one of many casualties in the search for a way to circumnavigate the globe. (Royal Museums Greenwich)

The search for a Northwest Passage fundamentally shaped the history of Newfoundland, where John Cabot landed in 1497 while seeking a northwestern sea route to Asia.

Although European sailors equipped themselves with the latest marine technologies, from agile caravels to magnetic compasses, their faith in the existence of a Northwest Passage was based on something much less modern: 1,800-year-old theoretical geography.

Taking only ancient philosophy and the Bible as evidence, Europeans were certain a navigable, ice-free Northwest Passage must exist, and their quest to find it would ultimately last centuries and cost hundreds of lives.

A symmetrical world

When Europeans first set sail into unknown waters, they had to rely on theory, rather than experience, to guide them.

Although Vikings had reached the island of Newfoundland around 500 years earlier, detailed knowledge of this territory beyond Greenland hadn't spread to other Europeans. Meanwhile, Marco Polo's account of his travels in Asia had done little to clarify how those lands could be reached by sailing westward from Europe.

With so little to go on, would-be explorers leaned on the most up-to-date conjectures of what lay on the other side of the horizon. These predictions were based on sources that, by our modern standards, were far from scientific: ancient philosophy and Christian theology.

The eighth-century Mappa Mundi d’Albi shows a symmetrical idealization of the world as it was known to medieval Europeans. The map is centred on the Mediterranean, with the Middle East at the top, Europe on the left, and North Africa on the right. (Médiathèque d'Albi-Centre Pierre-Amalric)

One of the few ancient texts dealing with geography to survive in Western Europe after the fall of the Roman Empire was Plato's Timaeus.

According to the Timaeus, a divine creator designed our universe following mathematical principles of balance and proportion. The very fact that the earth is a sphere — "of all shapes the most perfect," "the shape which contains within itself all other shapes" —  is evidence of its physical flawlessness.

The Old Testament seemed to corroborate Plato's views. The Book of Isaiah describes creation as an act of precise calculation by a god who "weighed the mountains in scales and the hills in a balance," who "measured the waters in the hollow of his hand, measured heaven with a span, and calculated the dust of the earth in a measure."

If the earth were created in divine equilibrium, so medieval and Renaissance thinking went, it stood to reason that its oceans and continents must be laid out symmetrically and in proportion to one another.

When 15th-century explorers brought word of the Americas back to Europe, it confirmed what most geographers already believed: that the continent of Afro-Eurasia must have a counterpart of equal size on the opposite side of the globe.

The top half of this 1489 world map from a Venetian edition of John of Eschenden's Summa astrologiae judicialis shows Eurasia and Africa separated by the Ocean Stream from a presumed southern continent of equal size. (Biblioteca Universidad de Sevilla.)

In 1487, Portuguese explorer Bartolomeu Dias rounded the Cape of Good Hope (the southernmost point of Africa) to reach the Indian Ocean, and, in 1520, fellow countryman Ferdinand Magellan navigated a strait through the southern tip of South America to the Pacific Ocean.

Under the prevailing theory of symmetrical geography, these journeys proved the existence of southwest and northeast passages. If there were open sea routes to the south of the world's continents, there must also be open sea routes to the north.

The wizard who trained England's explorers

Sixteenth-century English explorers received a thorough education in the principles of theoretical geography before setting sail, delivered by none other than famed occultist John Dee.

An advisor to Elizabeth I, Dee's astrological forecasts, communications with angels, and mystical writings earned him the nickname "the Queen's conjurer," and he tutored the leaders of every English expedition into northern waters in the second half of the sixteenth century, including Martin Frobisher, Humphrey Gilbert, and John Davis.

Steeped in ancient philosophy and Christian Kabbalism, he taught them the theory of symmetrical geography and used philosophical reasoning to justify the quest for a Northwest Passage.

John Dee performs an experiment before the English court in an oil painting by Henry Gillard Glindoni. (Wellcome Collection)

As strange as it may seem that a sorcerer had so much sway over English exploration, Dee's influence demonstrates the fine line between magic and science at the time. Though he may have been fascinated by mysticism, Dee was above all things a mathematician.

He used his mathematical talent not only to cast horoscopes and practise numerology but also to make astronomical observations, study Euclidean geometry, and develop new navigational instruments.

What we now think of as the natural sciences were, from the fourth century B.C. until the 19th century, classed as "natural philosophy" and considered a branch of philosophy writ large, just one more way of trying to better understand the world through observation and reason.

The theory of a symmetrical earth continued to drive exploration of the Canadian Arctic right up until Franklin's doomed expedition of 1845-48. His two ships, the Terror and the Erebus, were locked in impenetrable ice for three years, leading to the deaths of all 129 crew members by scurvy, starvation, and exposure.

The title page of John Dee's 1577 book on the art of navigation incorporates esoteric symbols, including the sun, moon, stars and a glowing tetragrammaton, to symbolize divine approval of British imperialism under Queen Elizabeth l. (Royal Museums Greenwich)

Ultimately, the Northwest Passage was only discovered by fluke in 1853 by Richard McClure and the crew of HMS Investigator, who were searching for Franklin's lost expedition.

They sailed through the Strait of Magellan in South America to the Pacific and entered the Arctic Ocean from the west. Then, when the Investigator was caught in pack ice and they were forced to desert it, they continued east by sledge and were rescued themselves by another British ship.

This second rescue ship eventually also had to be abandoned after becoming locked in ice, and everyone on board was forced to hike south to safety.

Although they had found the fabled Northwest Passage, they had disproved the theory of symmetrical geography, since, unlike its counterpart to the south, the Northwest Passage had not turned out to be reliably ice-free.

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