To start with, the definition of an allegory is that it is a type of writing that has a double meaning. On one level, it is a romance or adventure etc (e.g., Spenser's Faerie Queene) while on another level, it is a description of a moral, spiritual or political reality common to all people either actually or potentially (e.g., Animal Farm is an allegory of Soviet Communism that was then potentially universal to all people). Dr. L. Kip Wheeler of Carson-Newman College in Tennessee, USA, excerpts a passage from J. A. Cuddon's Dictionary of Literary Terms and Literary Theory, 3rd edition that is exceptionally illustrative. In brief, Cuddon explains, using this example: An Arabian folk fable involves a scorpion, a frog and a river and the scorpion's remark, "We're both Arabs, aren't we?" Cuddon explains that if the scorpion is renamed Mr. Treachery and the frog becomes Mr. Prudence and the remark is changed to "We're both men [or "of mankind"], aren't we?" the fable is changed to an allegory. The lesson of the adventure story is now symbolically applicable universally to all people. While it is not specifically stated in the definition of allegory that the characters have titles as names, e.g., Mr. Prudence, The Red Crosse Knight, Christian, etc, it is a common characteristic of allegory that they often do substitute names like Alice and Elijah and Chicago for titles used as names, like Miss Charm, Mr. Miracle and Emerald City.
Having said this, the genre that Ben Jonson's The Alchemist is analyzed under is that of farce. Critics consider that his characters, which are similar to the types in Chaucer's The Canterbury Tales, are farcical rather than allegorical. Jonson is using farce, with a whole catalog of "typical" characters, to mock the social element of swindlers and victims, a prevalent aspect of Jacobean society. "Typical" characters are those drawn from established literary types as opposed to fully realized individual characters. In farce (as in fable and allegory) this technique works rather well because audience members are familiar with these established literary types and can therefore all the more easily understand and appreciate the farce set before them, indeed, they may have on occasion been one of those types (e.g., victim or swindler) themselves.
In considering The Alchemist, it is important to note that as a critic and analyst, the reader may choose to read The Alchemist as an allegory if allegorical representations strike your perception of the story. Furthermore, a work of prose or poetry may be in whole an allegory or in part an allegory or have isolated passages or lines that are allegorical. Dr. Wheeler elaborates on this point more fully. When a reader gives an analysis or critical opinion of a work not typically considered allegory (e.g., The Alchemist) as being allegorical in whole, in part or even in one sentence, this sort of allegorical reading is called allegoresis. So in summary, The Alchemist is in the farce genre having characters who are well established literary types, not an allegory with allegorical characters, but an individual reading of allegoresis may find a unified allegory or partial allegorical sections or lines.
When determining if a story or literary work is meant to be an allegory one must identify symbols within the story that represent other things, and to see if the story relates to another meaning as well, one that is deeper than the obvious. In the book "The Alchemist" there are several deeper meanings that Santiago learn from his search for the treasure:
The journey in search of the treasure is a reward in itself: Santiago learn sthis after he has had the chance to have wonderful and risky adventures on his trip, met many new people, and seen sights such as the pyramids that he never would have seen had he not gone on his quest.
"There is no place like home" (Wizard of Oz phrase). Santiago is so busy dreaming and looking for the treasure that he fails to see the treasures at his home environments. However, he later learns this lesson.
If one does not ever follow ones dreams, then one can never attain them. Santiago is pushed forward by the King who tells him that many people stop going after the things they want because they just give up. However, nothing is gained then.
Symbols abound within the story. Fatima represents the gift from home that waits on Santiago’s return. The treasure and tip that Santiago seeks is a symbol of striving for one's dream.