Choose a philosopher from your course. Select the one whose ideas you understand most clearly or agree with the most.
Decide why the philosopher is writing to his student. For example, he may be answering a letter from the student in which the student asked for advice.
Review the philosopher's beliefs and determine how they apply to the subject of the letter. For example, if you are writing as Confucius to a student who needs help deciding whether to care for his elderly father or elope with his fiancee, remind the student that his duty is to put the needs of others before his own and explore the topic from that perspective. Review the primary sources from class for examples of how to apply the philosopher's beliefs to the problems of life.
Write an outline of your letter in which you plan your philosopher's argument in a logical order. Include as many details of the philosopher's beliefs as are relevant. In this example, Confucius's beliefs that children must honor the wishes of their parents, that people can best serve their societies by following social restrictions and that morality is the most important thing a person can master may all be relevant to his student's dilemma.
If you know details about the philosopher's personal history, include one or two details as supporting anecdotes for his arguments. For example, Confucius might refer to his own exile to support a claim that his student should not be afraid to do the right thing, even if it means accepting discomfort.
Write a draft of your letter in the first person, with "I" being the philosopher. Reread the draft and revise passages that are redundant or unclear.