In 1745, Hume received a letter from the Marquis of Annandale inviting him to live in his own home in London. Hume learned too that relatives and friends of the marquis were anxious to have him serve as a tutor and companion for the marquis, whose state of health, both physical and mental, seemed to require something of that kind. The remuneration which they offered Hume for his services was a strong inducement for him to accept. Up to this time, his very meager allowance had forced him to live in a most frugal manner, and now the prospect of a substantial increase was indeed a pleasant one.
Hume was too cautious an individual to accept an invitation of this kind until all of the details connected with it had been carefully arranged. This having been done, he went to London and spent one year at the home of the marquis. He was not altogether unhappy with the situation, but he was not as successful as he had hoped with his job of tutoring. At the end of the year, when his services were terminated, he felt that the chief value gained from this experience had been the amount of money that was now added to his small fortune.
Soon afterward, Hume received an invitation from General St. Clair to become a secretary to the military embassy to the courts of Vienna and Turin. This took him again to the continent, and while serving in this capacity, he wore the uniform of an officer. Again it was the financial return which he received for his services that constituted the chief benefit which he obtained from the appointment. He spent some time in each of the countries of Germany, Austria, and Italy, but the activities that were associated with military affairs were never his major interest. He wanted to continue with his literary pursuits and did so whenever the opportunity was available.
While still in the services of the embassy, Hume decided to rewrite certain portions of the Treatise of Human Nature, using a style of writing which he hoped would win for the materials a more favorable reception than the one given on the first publication of the book. The rewriting was done at different intervals for separate sections of the book. The first section was rewritten under the title Enquiry Concerning Human Understanding. It was published at Turin in Sardinia, but Hume tells us that its reception was only a little more successful than the earlier book had been.
