What prompted Gulliver to go on the third voyage?

Gulliver had the opportunity to serve as the head surgeon, as well as have his salary increased. None-theless, the most important reason for going on the third voyage was the adventure..... his thirst to see the world.

But repeating his visits often, expressing his joy to find I me in good health, asking, “whether I were now settled for life?” adding, “that he intended a voyage to the East Indies in two months,” at last he plainly invited me, though with some apologies, to be surgeon of the ship; “that I should have another surgeon under me, beside our two mates; that my salary should be double to the usual pay; and that having experienced my knowledge in sea-affairs to be at least equal to his, he would enter into any engagement to follow my advice, as much as if I had shared in the command.”

He said so many other obliging things, and I knew him to be so honest a man, that I could not reject this proposal; the thirst I had of seeing the world, notwithstanding my past misfortunes, continuing as violent as ever.