Can You Understand Any Philosophy Without Understanding All Philosophy?

A very funny cartoon:



One of the things I tell every one of my classes is that philosophy must be understood as a conversation. If you want to understand what a philosopher is really saying, you read his or her words closely, but you also need to know whom s/he is talking to. When you overhear a cell phone conversation in a restaurant, you can make sense of much of what is said, but some of the utterances are meaningless without knowing what the person on the other end of the discussion just said.

At the same time, arguments are sound or not because of their structure and the truth or falsity of their premises. Should it really make a difference what the argument is a response to? Every grad student gets sucked into this trap wherein one cannot begin philosophy anywhere past Thales.

But can you? Can you understand any philosophy without understanding all philosophy?