What is the theme or lesson of Santiago carrying around his jacket and how does the jacket embody or symbolize that theme?
Coelho's The Alchemist is a symbolically rich tale. Most of the symbols are explained in one way or another. The jacket doesn't seem to be one of the many Christian or Arabic symbols, though. It seems merely to be an item of clothing. The jacket first appears on the first page of the book as Santiago uses it not to get warm, but to sweep up his resting spot under the broken roof of the abandoned chapel. This opening scene is set in summer when the boy is annoyed that he has to carry his jacket. But then he remembers that he needs the jacket in the winter for warmth and decides not to take it for granted. Since Santiago is a shepherd, he doesn't have a home that he goes back to each night. It seems to be the custom of his time that shepherds traveled around and never settled down; so, having the jacket throughout the year was a necessity. The boy realizes that the jacket is a symbol and reminder of how the seasons of life change. He is then grateful for his jacket even though it is summer at the present time of the book's opening.
Another parallel drawn from the jacket is that the boy realizes that the jacket has a purpose and so does he. He feels that his purpose is to travel even though his parents wanted him to be a priest. "But ever since he had been a child, he had wanted to know the world, and this was much more important to him than knowing God and learning about man's sins" (8). So, just like the jacket represents warmth in the winter as its purpose for existing, Santiago feels that his purpose in life is to know the world.