Percy the Small Green tank engine was bored. Thomas and Toby were running their passenger trains while Daisy was on the mainline.
As he idled in Knapford, watching the clock tick by, a question flew into his funnel. His driver had asked this some time ago to keep Percy's mind from wandering while he worked.
Soon Edward entered the Station with coaches. Edward was a smart old engine, and Percy approached him with the question.
"Hey Edward!" he called.
"Yes?" answered the Blue Engine.
"If you replace every part of an engine, is it the same engine, or is it a new one?"
For once, Edward didn't have an answer, "I don't know Percy. What made you think of this?"
"Well, my driver asked me just yesterday and I was wondering if you knew the answer."
"Unfortunately, Percy, I just don't know. I must be off now! I'm taking these coaches to the Works to be repaired," and with a loud whistle, he was off.
"The works!" exclaimed Percy, "Of course! Victor may know about rebuilding engines!" He sped off to catch up to Edward.
The little tank engine whistled with excitement as he raced down to the Steamworks. He kept thinking of his question while he travelled down to Crovan's Gate.
Victor was there and he was surprised to see Percy there, "Percy, my friend, what is the problem?"
"Nothing Victor, I just have a question. 'If you replace every part of an engine, is it still the same engine?'" he asked as he screeched to a stop.
"No, it's not!" answered Kevin as he skidded around the corner, "All the parts were replaced!"
"Kevin, what did I tell you about horseplaying?" scolded Victor, "And Percy, it is the same engine. When you rebuild an engine, it's called an overhaul. We do them all the time in here."
"Ah," sighed Percy, "So it wasn't that hard of a question."
However, he wasn't satisfied with that answer and he sped off to go find Henry. He met him at Knapford before he left for the evening.
"Henry! You've had an overhaul, right?" he asked as soon as he stopped.
"Why yes Percy. After I had my accident with the Flying Kipper, the Fat Controller sent me to the mainland to be rebuilt," Henry answered.
"Oh, and how did you feel afterwards? Did you feel the same or different than you did before?" Percy continued.
"Well I felt like a brand-new engine, from my buffers to my tender!"
"I have two answers for this question," Percy wheeshed sadly as he puffed back to Knapford.
All afternoon, he asked the other engines on the Island. Half answered yes, and half said no. Percy soon arrived at the sheds and asked, with the same mixed results. All the engines stopped talking as soon as the Fat Controller pulled up to the sheds.
He looked at Percy, "Percy! Where have you been? You've had several trains to pull and no one has been able to find you!" he scolded.
"I'm sorry Sir. I've just been trying to answer a question."
"What was this question?" asked Sir Topham Hatt.
"If you replace every part of an engine, is it the same engine, or a new one?" Percy asked.
Sir Topham Hatt froze as he thought. The other engines had never seen him puzzled before and they laughed. He gave them a stern look.
"Percy, there is no answer to the question. It's a paradox, that means there can be many answers and none are entirely correct."
Percy gasped in amazement. He had never heard of an unanswerable question, but he was glad that he had some sort of answer. At least for now.
And that is the story of how Percy learned that some questions just don't have an answer.
The End