I don't think the definition of "obvious" you think is obvious is obvious.
At least, I think it's obvious it's not obvious it's obvious.
The poem which traditionally accompanies this koan refers to a particular Chinese folktale.
If I make a reference to a poem that mentions sour grapes, how could you understand my meaning without looking up the fable by Aesop?
Sometimes things in plain sight are hardest to find, and the obvious is as hard to see as the nose on our face.
Joshu Washes the Bowl
A monk told Joshu: `I have just entered the monastery. Please teach me.'
Joshu asked: `Have you eaten your rice porridge?'
The monk replied: `I have eaten.'
Joshu said: `Then you had better wash your bowl.'
At that moment the monk was enlightened.
Mumon's Comment: Joshu is the man who opens his mouth and shows his heart. I doubt if this monk really saw Joshu's heart. I hope he did not mistake the bell for a pitcher.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.