Allegory Writing: The Art of Philosophers.

Allegory (a literary device) stands as a form of writing which contains two key traits; symbolism and imagery. These two traits, along with theme and setting, set a desired message(s) in the story; an underlining commentary.

This form serves as a philosophical literature form to express concepts and content in a more tangible fashion to the reader/audience. It serves as a relay for the philosophical message of the writer, whilst having a strong aspect of open-ended interpretation.

The key to writing allegory is to first set the desired message(s). It is important to note that allegory writing requires an open-ended and open-interpretive symbolism and imagery, which is to say that two readers may draw different conclusions of the author's desired message(s) and subsequently the entire underlining commentary.
The message can be simple (i.e.; political issues, poverty, war, etc) or it can be a complex message (i.e.; Albert Camus' "The Plague" defining and expressing the frailty of human morality.)

Although, that said, allegory falls under no strict rules, so an experienced and skilled author may do something outrageous or riskee. For more novice authors however, starting with one underlining commentary is recommended.

Some recommended reading I'd suggest for those looking for clear allegoric literature would be

Albert Camus: The Plague - by Albert Camus
-Human Morality

Sonny's Blues - by James Baldwin
-Racism
-Poverty
-Drug-use

Passing - by Nella Larsen
-Racism
-Racial/Cultural Identity

The Standard of Living - by Dorothy Parker
- American Dream
- Wealth

Furthermore, note that one underlining message does not mean a single conclusion or interpretation of that message. A good allegory author is an author who can create multiple ways of seeing the symbolism and imagery in his/her work, and subsequently more than one way of seeing the end result of the overall message.

With the underlining commentary taken care of, I shall now move your attention to symbolism and imagery, the building blocks of allegory.
In the book "Sonny's Blues", there is a great example of imagery being used to convey a symbolic and plot-oriented concept toward the underlining commentary. The protagonist/narrator sits in the New York subway going to work, reading the paper about his brother being arrested for drug-use. The Harlem area is culturally attributed with poverty and violence during the time of this book. The narrator describes "Then perhaps I just stared, at the newsprint spelling out his name, spelling out the story. I stared at it in the swinging lights of the subway car, and in the faces and bodies of the people, and in my own face, trapped in the darkness which roared outside."
This symbolism uses (possibly) the "swinging lights" and "darkness" as references to the protagonist's protective emotional isolation. The car and the light "swinging", which can refer to his own emotional attempt to fight back the darkness and the car standing for his bubble reality. The darkness could stand for the dark nature of the real world around him.

In light of this form of writing, one last thing must be known to properly appreciate the powerful influence of this form.
Allegory can also refer to subtle uses of theme and imagery (books), lighting, texture and non-verbal expression (film and visual art). In most modern art of all types, this form is used in various ways.
Imagine you watch a science fiction film and the last scene is the death of the protagonist, however those who stand around him are military personnel in shaded armour and red visors, guns in a standby position, flanked around the area as the camera goes by following the protagonist and his co-protagonist. The music is an epic-heroic sad theme. What do you think you would draw from this scene?

In this case, the psychology and stigmas of your perception are being royally *Blank* with. Why? Because everyone interprets black and red as malicious, and everyone associates armed soldiers with war. Put the two together and you have malicious violence. Now, mix this with a sad and heroic song, along with the death of the story's protagonist and you're left with a variety of conclusions.
The strongest allegory from this in my opinion would be that the co-protagonist, who is walking before the body of her partner, is being symbolized as evil. This allegory draws that the death of the protagonist has drawn out evil in the co-protagonist, or worse she was evil to begin with.

Practice using imagery, theme and setting to express an underlining commentary and you'll master allegory.

Thank you very much for your time. I hope to contribute more in the future and I hope even more to read many of the allegorical works that members of the community write.