(Original Review, 1980-09-24)
Before we ask "Are dolphins intelligent?" we must ask "What is intelligence?" Doug Hofstadter, in his book "Gödel, Escher, Bach: The Eternal Golden Braid", presents a way of looking at intelligence that is not as restrictive as most current definitions. (I highly recommend this book to anyone, by the way. It is published by Basic Books in hardback, and is worth whatever you may pay for it.) He makes a good argument for the claim that intelligence is a consequence of the complexity of organization of the nervous system of an organism.
If you're into stuff like this, you can read the full review.