The pursuit of happiness is a central theme of the novel, The Alchemist . Please someone explain in detail?

Dreams in the sense of "goals" or "pursuit of happiness" constitute a major theme. Santiago's dream of the treasure provides him with a goal; Santiago resolves to find the treasure, and by his decision to pursue this goal he is able to realize his Personal Legend. Thus, Coelho plays with the dual (and of course linked) meanings of the word "dream", as both visions during slumber and far-reaching objectives. In this sense, the message of The Alchemist could be described as follows: everyone needs a dream. The vulnerable periods of Santiago's journey are when he has no clearly defined goal. This is true when he finishes working at the crystal shop, as well as when he contemplates staying at the oasis with Fatima. Both times he thinks about desisting, but winds up carrying on unswayed.

As a counterpoint, we can think of the shopkeeper, who is afraid to realize his dream of going to Mecca. He does not want to achieve his dream because he feels that it is the only thing keeping him looking forward to the future. Santiago tries to show him that if it is his destiny, he has no choice but to seek it out, or else he is not living. In this way, The Alchemist is not about what one should dream, but merely that one should dream.