the letter...

In "letter to Sir Walter Raleigh" Spenser wanted to express his feelings and messages through a different way. He did not want to write the content explicitly but he wanted to do it in hidden way. He starts the letter by saying it is an allegorie, which means people will not get the real message just by reading it but they will have to interpret the meaning that is behind of the sentences. Maybe he decided to write the letter that way because it may be in wrong hands. So, if someone would read the letter he/she wouldn’t understand the real meaning of it.
He mentions more than an important character in his letter. He refers to King Arthur, Homer and Aristotle. I think he decided to mention these people because he wanted to show some characteristics through them. They were and still are people very known by everybody in the world, so who better than them to express the characteristics he wanted to express?
I do really think the only purpose of his letter was to let W. Raleigh know about the topics he wanted to say. Besides, Spencer did not want that every single person know about the real meaning of the letter, so he decided to write it in way that W. Raleigh could understand but not the rest of the people.