Douglas Adams also said, "It is a mistake to think you can solve any major problems just with potatoes." Are you really going to put alot of analytical thought into someone that puts forth the bizarre and fanciful quotes that he does? Especially when penned in a book such as The Hitchhiker's Guide to the Galaxy?
How else would one explain flying? Jumping in the air and flapping as hard as you can? Leaping off a building and hoping to catch a thermal? His explanation is better than anything out there, so accept it at face value. :)
He also said: There is a theory which states that if ever for any reason anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.