Long time ago, a young man paid a visit to a Zen master, asking for truth. The master welcomed young man by some tea: he poured tea from tea pot into tea cup. When the cup was full, he continued pouring, so tea overflowed. The young man asked: "The cup is full, why are you still pouring?" Answered the master: "You are right. If the cup is full, I would not be able to pour fresh tea in. Same as our heads, if they are full, now new ideas could be put in. So, do you have an empty head?"
This is a legendary tale in Zen history. In life I realized, so often our existing beliefs or knowledge would not only prevent us from learning new knowledge, as this Zen story implies, they also distort our observation. Some time we think we saw "fact", but we barely saw what we wanted to see. How I took this photo of gas light lamp is a perfect example:
One day I drove past an apartment gate I saw two gas light lamps hanging on each side of the stone gate wall. I decided to go back to take some pictures of them. In my memory, the frames of lamps were all black, and I was glad because the contrast between black lamp frames and stone gray background would make a perfect image. So I went back the second day with camera. To my disappointment, the lamp frames were not black, but steel gray, and they didn't make good contrast against background as I anticipated. I wonder if the dust on lamp surface make lamps looked gray, but after I checked I found that's not true, because it was rained earlier, the surface of lamps were perfectly clean. But why I remembered they were black? Then in a flash of moment I realized why: because all gas light lamps in my memory were black! That's why! That's how my "knowledge" distorted my observation: I "knew" gas light lamps were dark colored so I "saw" dark colored gas light lamps.
So this experience reminded me the Zen story of tea cup. I think the inspiration of this story is invaluable to human intelligence, that is, only when we empty our mind, put what we think we already knew aside, can we have fresh minds and eyes for truth.