Desmond, who was a real town dweller, drove his car into a ditch when out on the country roads. Luckily, a local farmer was passing by with his big strong horse called Dobbin.
He hitched Dobbin up to the car and shouted loudly, "Pull, Dolly, pull!" Dobbin didn’t move one inch.
Then the farmer yelled, "Pull, Robbie, pull." Still Dobbin failed to respond.
Once more the farmer commanded in a stentorian voice, "Pull, Ringo, pull." Again - nothing.
Then the farmer nonchalantly and quietly muttered, "Pull, Dobbin, pull." Immediately the horse easily dragged the car out of the ditch.
Desmond was very appreciative but also very curious. He asked the farmer why he called his horse by a different name three times.
The farmer whispered by way of reply, "Oh, Dobbin is blind and if he thought he was the only one pulling, he wouldn’t even try."