It is like a person in pursuit of a bird. He looks at the branch of the tree which is still shaking after the bird has flown from it. He says, "Oh, here is the bird", but he is only looking at the branch trembling hither and thither after the bird has sat there just for a moment. He calls the branch the bird. Another person may see a branch moving, but this time the branch is so strong that the bird could not possibly have moved it. Not understanding this, he thinks the bird sat on that branch. Thus it is with the truth.