"A great sage who was a very close adviser to a powerful king had an argument one day with some of the king's other advisers. He felt that it was not possible to change the nature of an animal, whereas the others thought it was possible, through practice and teaching. They decided that they were going to prove this to him by training an animal.
"A few months later they sat down with the sage before the king and at the clap of their hands a cat came in, carrying trays of food. It carried the food onto the tables. After they had finished the first course, it removed their dishes and throughout the whole meal acted as a human waiter.
"At this point they were sure that they had finally proven the sage wrong. 'See,' they said, 'you can change the nature of an animal.'
"The sage then reached into his bag and pulled out a small box. He opened the box and out jumped a mouse. The cat dropped all the dishes and all the trays and started running after the mouse.
"Smiling, the sage looked at the other advisers and said, 'You can make the cat or any other animal act differently, buy you cannot change the internal nature of a cat or any other animal."
Excerpt from:The Way; Using the Wisdom of Kabbalah for Spiritual Transformation and Fulfillment, by Michael Berg, John Wiley & Sons, Inc. 2001