根据下面材料回答48-50题：
Passage Four
Magic（魔法）often forces us not to believe our own eyes or even appears to be breaking the laws of physics or nature!The word“magic”has many different meanings．When a bird appears in a hat or when someone declares that he could see into the future--both can be called magic．When a sick person suddenly becomes well or a well person（or even animal）becomes ill，magic is the cause．The British author Terry Pratchett uses magic a great deal in his popular Discworld series of books．
Magic has always been used for fun．People enjoy working out in which cup the little ball is or how he knows which card l was thinking of．Harry Houdini was one of the first world-famous magicians—famous for escaping from deadly situations．Recently David Copperfield，or David Blane，has become very popular for his“unbelievable abilities”，such as making the Statue of Liberty disappear or rise．
Magical rings and three—headed dogs may not be real，but does this mean nothing magical really exists？Can you always explain how the magician has done the card trick？Maybe it is better not to explain，but to leave a little magic in our lives．Pick a card．any card......

The author explains what magic is in paragraph 1 by （）．