Sights as a motif
Boswell is motivated almost purely by the prospect of witnessing something amazing. His thirst for landscapes pulls him forward in the story, and when his traveling partner tries to take less scenic routes, preferring paths that lead to fun activities, Boswell and he will quarrel. For Boswell, there is almost no reason to travel except to witness the grandeur and beauty of nature. The motif symbolizes Boswell's attachment to wonder and awe, and it signifies a certain quality of nature to bring forth amazement.
The journal as a symbol
To Boswell, the journal symbolizes the sacredness of his travels, because the travels are a kind of pilgrimage to him. Instead of finding just one place, though, he finds a whole host of places, so in order to catalog them and record his time with nature, he writes his experiences down. The journal is a symbolic reference to the function of written language, because he obviously uses the journal as a tool for recording his human experience, and now, over 200 years in the future, the reader can see that the journal literally accomplished the task, perhaps more than the author even intended.
Lady Macdonald as an archetypal encounter
Although Lady Macdonald is a real person, that doesn't stop Boswell from having an archetypal experience with her. He finds himself toeing a line in Sir Alexander's company, as if he would rather Lady Macdonald leave her husband and become Boswell's. This signifies entitlement, because Boswell feels his experience of Lady Macdonald is more true and important than her own husband's experience. She takes on a mythic quality because he cannot have her. To him, she comes to represent his longing for what he cannot have.
Johnson, the friend
The foil of Boswell's emotional experience is his travel companion, Samuel Johnson. Johnson is very different than Boswell, so they provide interesting counterplay to each other's opinions and experiences, which Boswell records. Also, they are like brothers, because as Boswell gets grumpy or disappointed, they often descend into conflicts. Johnson doesn't see the religious wonder of nature, and he prefers activities like sports and games. He is easily bored, and he doesn't like sitting still in silence, for instance.
The visit home
The journey guides the principal figures in a circuit from Edinburgh, through the country, into the Hebrides mountain range, and then to Auchinleck, Boswell's home estate, and then back to Edinburgh finally. The fact that Boswell does not consider his family estate to be his home is evident, because he passes through it on his way to Edinburgh. This is symbolic, because it explains the attachment Boswell might have with nature. He has removed himself from his family, so that nature feels more like home to him than his own estate, and perhaps this signifies some of the origins of his opinions. Either way, the visit home bears archetypal significance—especially since he is literally ending a journey.
