The Buddha teaches his uncle Mahanama the significance of understanding sense desire [kaama], sense objects [forms, ruupa], and sense-experiences [vedana].
Read the Sutta
Index to available translations: AN 3.124
This is a very deep sutta in the form of a very short exchange between Gotama and Bhara.n.du the Kaalaaman.
The result of the exchange is that Bhara.n.du the Kaalaaman gets up and leaves town never to be heard from again.
Woodward expresses perplexity as to the reason for his departure, Bhk. Bodhi does not comment. My suggested explanation is:
This departure is an act of inwardly re-directed anger (like suicide) at being made to face embarassment at being shown up in front of an important personage.
The lesson here is to see how he was shown up - that is, this was not simply a case of his being contradicted three times and taking offense at an afront.
Bhara.n.du's reaction shows that he did not understand the significance of comprehension of the realationship between sense desires, forms and sense-experiences.
Holding the position that the result of understanding all three is the same is thinking that understanding sense desires includes understanding as well forms and sense-experiences. That is, that the same desire to experience a sensation from a given sense organ and sense object will always produce the same sense-experience.
By aserting this position he is also claiming to understand the three.
But if Bhara.n.du had understood the relative relationship of sense desire, form, and sense-experience, he would have seen what Gotama was doing (which was showing him that the same sense desire and form combination was producing different sense experiences at each repetition) and he would have seen the error in his thinking and in spite of his embarassment, would not have felt anger (at the unpleasant mind sense-experience of being contradicted), could have seen the value of the lesson (that any sense desire/form situation could give rise to three different sorts of sense-experience depending on one's point of view) and could have become a disciple of Gotama.
This entire course of events looks like it was forseen by Gotama, but still he had to give Bhara.n.du the opportunity to take another path.
He didn't say in the beginning: "Set me up with lodgings at the ashram of Bhara.n.du the Kaalaaman.
He could not have remained silent after Bhara.n.du's interjection or that would have misled Mahaanaama.
He let fate take it's course and played out his part as was required by the situation.
The fault was really Bhara.n.du the Kaalaaman's for putting himself between Gotama and Mahaanaama.