“But why must everything change all the time?” pressed Lucy, stroking the blue dog in her lap all the while.

“If it doesn’t change it’ll all become boring,” the Professor immediately replied. “We can’t laugh at the same jokes forever. New jokes are a type of change. If we get fed up with an old joke then that too is a type of change.
 
“What you thought and did at three years of age is different to what you will like doing when you are twelve or twenty or sixty. Why? -Because of change. What you do at your age is different to what I did when I was that age. When I was your age I wore short trousers and was thrilled if I received a potato on Christmas morning. You wouldn’t be happy with that and that’s because things have changed. If everything stayed the same there would be no progress. None of us would get anything done, ever, because there would be no point in doing anything if everything was going to stay the same anyway!”