He also had an article in Rolling Stone in which he discusses the fact that the public's right to the Commons (i.e. a healthy, livable environment) goes back all the way to Rome's Code of Justinian and the Magna Carta.
He presents a comprehensive condemnation of the Bush record, and makes his case from a moderate position that calls on fiscally conservative, free-market ideology (basically making the Econ 101 argument that pollution imposes costs on the public, hence permitting it without consequence is equivalent to a subsidy) and the Jeffersonian vision of a nation of indepedent freeholders (what has in the modern age become "the middle class") as well as an eloquent appeal to spiritual/religious sentiment: "God talks to human beings through many vectors ... but nowhere with such clarity and texture and grace and joy as through Creation."
I think of the current generation of Kennedy's, he's probably the one who has inherited the most of JFK and RFK's knack for rhetoric...
(Of course, I happen to think it's a fallacy to regard humanity as not being an integrated part of "Creation", "Nature", etc. The notion of the "artificial" is itself the most artificial of humanity's inventions. We have no meaningful future except as part of the natural world -- as he said elsewhere in his speech, the US economy should be regarded as "a wholly owned subsidiary of Nature".)