In the last quarter of the sixteenth century, John Dee, Sir Humphrey Gilbert, and John Davis, became key advocates of the English search for the a northwest passage. Before the English explorers set out in search of such a passage, they needed reasons to believe that there might be an open sea route to China. These three men were instrumental in constructing rational arguments for the existence of a northwest passage. They found Plato’s Timaeus a particularly valuable source for justifying and validating their belief in the existence of the passage. Although the majority of received classical lore indicated that the Arctic regions were neither inhabitable nor navigable, paradoxically it was their familiarity with the classics that caused these English writers and explorers to develop their own carefully reasoned theoretical arguments for the existence of a northwest passage. In doing so they helped to spur English arctic exploration from thought into action.