About this passageMāluṅkyaputta, a monk, has told the Buddha he will leave the training unless he is first given answers to ten questions: whether the cosmos is eternal, whether it is finite, whether the soul and the body are the same, what becomes of an awakened person after death. This simile is the whole of the reply. The discourse goes on to say the questions are left undeclared not because they are forbidden but because settling them does not stop anything hurting.
Suppose a man was struck by an arrow thickly smeared with poison. His friends and colleagues, relatives and kin would get a surgeon to treat him. But the man would say:
‘I won’t extract this arrow as long as I don’t know whether the man who wounded me was an aristocrat, a brahmin, a peasant, or a menial.’ He’d say: ‘I won’t extract this arrow as long as I don’t know the following things about the man who wounded me: his name and clan; whether he’s tall, short, or medium; whether his skin is black, brown, or dingy; and whether he comes from such-and-such village, town, or city. I won’t extract this arrow as long as I don’t know whether the bow that wounded me was straight or recurved; whether the bow-string is made of swallow-wort fibre, sunn hemp fibre, sinew, sanseveria fibre, or spurge fibre; whether the shaft is made from a bush or a plantation tree; whether the shaft was fitted with feathers from a vulture, a heron, a hawk, a peacock, or a stork; whether the shaft was bound with sinews of a cow, a buffalo, a black lion, or an ape; and whether the arrowhead was spiked, razor-tipped, barbed, made of iron or a calf’s tooth, or lancet-shaped.’
That man would still not have learned these things, and meanwhile they’d die.
In plainer words
A man is shot with a poisoned arrow. His people fetch a surgeon, and he says he will not have the arrow pulled out until he knows who shot him — the man's caste, his name, his height, his complexion, his village — and what the bow was made of, and the string, and the shaft, and the feathers on it, and the arrowhead. He dies without finding out. The Buddha's point is not that the questions are stupid. It is that the arrow is in you now.
A restatement in modern English, written for this collection. The passage above is the text; this is one way of putting it.