Once upon a time a fox startled a young rabbit in the woods. The rabbit said "What are you?", and the fox said, "I am a fox, and I can eat you up in a single bite if I want to."
"Really? Can you prove you're a fox?" asked the rabbit. This question startled the fox so much that he couldn't think of a reply.
The rabbit said, "Well, it's certainly odd that you have no reply, but if you can come up with written proof that you are a fox, I suppose I will believe you."
The fox decided that the lion would be able to help him with this problem, and in fact, the lion gave him a lovely certificate declaring that he was a fox. The fox returned to where the rabbit waited for him and started to read his new document out loud. The phrasing was so elegant and pleasing that he didn't notice, as he was just coming to the end, that the rabbit ran into its burrow and disappeared.
The fox went back to the lion's den, but there was already a line. In fact, a deer was saying to the lion "I want to see written proof that you are actually a lion". The lion replied, "If I'm not hungry, I don't care what you think. And if I am, you won't need any proof in writing from me!"
The fox complained, "Why didn't you tell me to say that to the rabbit? I wouldn't still be hungry now!"
"I'm so sorry," said the lion, "You should have told me you were talking to a rabbit. I thought you must have been talking with a human being, where these idiotic certificates are all the rage."