Kelsey is extremely knowledgeable of Greek philosophy. That being said, he expects a lot from his students. Unlike other professors that tell you just what the greek philosophers are trying to say in their texts, Kelsey tries to make you grasp the material yourself. That doesn't mean his lectures don't help you--lectures will only give you a broad understanding of the subject, so that in order to really understand what Kelsey's trying to explain, you have to peruse the text. If you like a good challenge in philosophy, you should definitely take this class. He's a great professor.