A Moveable Feast is a collection of Hemingway's reminiscences about living in Paris as a young man. In it, he reflects on the various places, people, and activities that mark his life there. It was a rich time for literary Americans, a significant number of whom resided in Paris and communicated extensively with one another. Naturally, Hemingway's emotions are greatly impacted by the experience of living in Paris at this point in his life.
An example I like is from the chapter entitled "A False Spring." On pages 56 and 57, Hemingway is walking and talking with his wife, when he realizes they are hungry. They decide to go to a restaurant—Michaud's—to eat. There, while having an engaging conversation, Hemingway realizes that the feeling had not been mere hunger after all. He says, on page 57: "When we had finished and there was no question of hunger any more the feeling that had been like hunger when we were on the bridge was still there when we caught the bus home." That inexplicable feeling remained with Hemingway all night, even in bed, after making love to his wife, and continued as he brooded through a sleepless night. He reflects on that feeling, wondering at its power. In the end, he concludes that it is because of Paris.
On page 58, he explains the mood like this: "But Paris was a very old city and we were young and nothing was simple there, not even poverty, nor sudden money, nor the moonlight, nor right and wrong nor the breathing of someone who lay beside you in the moonlight." Paris, indeed, is a moody city, always playing with the emotions. As Hemingway says, it is not so simple to identify a feeling, even one so seemingly straightforward as hunger.