books.google.com - From the Reviews: .,."He (the author) uses the language and notation of ordinary informal mathematics to state the basic set-theoretic facts which a beginning student of advanced mathematics needs to know. ...Because of the informal method of presentation, the book is eminently suited for use as a textbook...http://books.google.com/books/about/Naive_Set_Theory.html?id=x6cZBQ9qtgoC&q=arithmetic&utm_source=gb-gplus-shareNaive Set Theory