 The Royal Society, and especially Alexander Dalrymple, believed that "Terra Australis" must exist, and that Britain's best chance of discovering and claiming it before any rival European power would be by using Cook's innocuous Transit of Venus mission.Cook, however, had his own personal doubts on the continent's existence.With the help of a Tahitian named Arioi and a navigator named Tupaia, who had extensive knowledge of Pacific geography, Cook reached New Zealand on 6 October 1769, leading only the second group of Europeans known to do so (after Abel Tasman over a century earlier, in 1642).