He earned his Master's degree in 1750 and received a scholarship which enabled him to travel to Göttingen for further study, amongst other subjects in Asian languages under the famous professor Johann David Michaelis.
The expedition to Arabia was Michaelis' idea; he was studying the Bible from comparative historical and linguistic perspectives, so determining details of life in the Middle East was important to his work.
When von Haven heard that Maronite monks from Syria were teaching at a college in Rome, he obtained a scholarship to go there and learn Arabic from them.
In his absence, the other members of the expedition were appointed by Michaelis and the foreign minister, J. H. E. Bernstorff: the botanist Peter Forsskål, a pupil of Linnaeus, the mathematician and astronomer Carsten Niebuhr, the engraver and miniaturist Georg Wilhelm Baurenfeind, and the physician Christian Carl Kramer.
On 11 February, the ship was forced once more to return to Helsingør, and von Haven decided to travel overland to Marseilles and join the expedition there.
For example, he watched Professor Kratzenstein in Copenhagen make plaster casts of inscriptions and demonstrate how he cut off a block of inscribed marble.
He had enjoyed himself in the city, going to theatrical performances and concerts and visiting prominent people, and writes in his expedition journal that he "wished they had stayed away for another 14 days".
There and in Cairo, von Haven made the vast majority of the manuscript purchases which formed part of his professional duties on the voyage.
However, they were led astray by their Arab guides and were not able to see the inscriptions on the mountain; and the monks would not let them into the monastery because they did not have a letter from the Patriarch of the Greek Orthodox Church.
Bernstorff was dissatisfied with the response and wrote back that he expected better results, but since the post between Denmark and Egypt was slow, his letter did not arrive until long after von Haven's death.
On the afternoon of 25 May, with an unsteady hand, he wrote the last entry in his travel journal: "25 May 1763, morning: after midday God gave me, I believe, a blessed ending.
The Arabian expedition is today mostly known through the writer Thorkild Hansen's 1962 documentary novel Det lykkelige Arabien (literally, Arabia Felix).
These letters are concerned only with personal matters and not with the work of the expedition, which has greatly impacted Hansen's picture of von Haven: he appears in the book as someone who thought only about comfort and good food, and complained constantly about bad health.
His problem was, as Hansen states in his novel, that the expedition spent most of its time at sea or in barren wastes and that there was little for a philologist to do in such places, while there was much for a cartographer and a botanist to do.
[8] For literary reasons Hansen demonised von Haven: his negative aspects were to contrast with the heroes Niebuhr and Forsskål.