Any of the philosophers mentioned, but may not be biographical.
The subject of any of the sections of any of the chapters, but such a essay needs to be quite specific and reflect a thoughtful viewpoint.
2. Any of the philosophers mentioned, but may not be biographical. It needs to be about the philosophers philosophy. E.g. if you write on John Lockes political philosophy, you must demonstrate the distinction between his and one or the other of political philosophers or traditions.
3. An example of a good essay is a discussion of how John Lockes political philosophy is manifested in The Constitution of the United States of America.
4. Another example would be to compare the views of one pre 20th century and one 20th century philosopher on the nature of the self.