There was once a blind man that knew sign language and a deaf man who could speak. At one time, both men had all of their senses but various accidents led to their various and many infirmities.
One day, the two were sitting in park on the bench and a car near the road came and went. The blind man signed to the deaf man, 'What does that vehicle look like?'
The deaf man replied, 'It looks like a black sedan. It was very ordinary. I suppose the vehicle was rather humble.' Then asked, 'What did it sound like?'
The blind man signs back, 'I was alerted to it by the large sound of the engine; but if you described it to me accurately, then I cannot make sense of it. How does a sedan cause such a commotion?'
The deaf man thought it over. Finally he answered, 'Such a great commotion could not reasonably come from this kind of vehicle if it were not intended by the owner. Judging by my experience and your description, I can guess that the owner could be a master mechanic or we are deceived and he used another mechanic. But that raises a new question; who would put their time or their money into making that kind of car loud?'
The blind man signed back, 'This man, whether by himself or through another, has made himself known to us by the sound of his vehicle and the question raised by it. If either one is true, it doesn't matter to my life here. I will never be able to fully realize this car or know the truth of it's looks because of how I am injured; but I know there is a car and it is loud.'
Again, the deaf man pondered the response. Finally, he spoke, 'And because of my infirmities I can see there is a car. I cannot hear it, but I can trust in the friend I have to describe to me what it sounds like. And more than that, if it is making a sound, I will feel the vibrations if the sound is loud enough and unique enough.'
The blind man replied, 'Wait, what are we talking about?'