Life and death
Goethe's diary is a record of lived time, and many of his reflections on his time are oriented around death. He quotes a deathly motif, "et in Arcadia ego," which loosely means, "even should I enter paradise." He discusses his responsibilities back home where he serves his community as an authority figure in several institutions, and he observes the way his sense of self changes as he travels away from those responsibilities. When he has departed far enough, he finds that what he gains is an appreciation for the value of each moment, knowing that his time on earth is fleeting.
The importance of travel
As the title of these published diary entries suggests, the value of a Journey is one of the central thematic questions in the book. The implication of departing one's home to endure a journey and then return is that Goethe is on a kind of hero's journey, and he notices that in his writing, pointing out similarities between his travels and the books he has read and written. His travels take him through beautiful landscapes and many foreign cityscapes as well, so that he has a broader appreciation for the shape of life on earth.
Happiness and paradise
Ultimately, the most important thematic consideration of his writing is his happiness. He struggles at times to understand what happiness might mean within the context of his own life. For instance, he has achieved a great deal of rapport in his community, and many view him as a pillar of several institutions. One might think he would be happy with such power, but the question of happiness is the subject of much consideration throughout his travels. In the end, he decides that what he's traveling in search of is a paradise that doesn't exist on this earth during this life.
