Original: "The drama is the most social of literary forms, since it stands in so direct a relationship to its audience."
Plagiarizing paraphrase: The theater is a very social genre because it relates so directly to its viewers.
Fair-use paraphrase: Levin claims that we experience the theater as the most social form of literature because we see it unfold before us.
"Your own words" means your own sentence structure too, not just the substitution of synonyms. If paraphrase is going to be that close, then why not just quote verbatim? Paraphrase has to add something; your own voice or perspective, an added explanation, a greater degree of concision or clarity. It is not meant to be a simple replacement of words. The point is not just to avoid plagiarism, but to integrate perspectives, compare your ideas with those of others.
Aside from Williams's book, I also recommend Claire Cook's Line by Line, a guide to writing that helped me a good deal at one point in my career. I do not recommend Strunk & White, a book that is at best vague and unhelpful, at worst misleading and inaccurate. Go to Language Log if you want the full critique of S&W.