Brahman Dona comes to Gotama intending to criticize him for not rising up for Brahmins and is given an education as to various sorts of Brahmins.
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Index to available translations: AN 5.192
In various places in the Suttas, brahmins approach Gotama telling him that they have heard that he does not rise up for elder brahmins. They, being old brahmins, see that he does not rise up for them, criticize him for his lack of courtesy and are usually given a lecture on what constitutes an 'elder' or the person who should be shown such veneration. That is, their criticism is answered directly.
Here Dona, who is apparently not an old brahman, but simply brahmin born and educated, observes that Gotama does not rise up for him and concludes that what he has heard is correct and launches into his criticism. But here Gotama's response is very subtle. He speaks to Dona of the doctrines laid out by Dona's own authorities concering what constitutes brahmin worthy of veneration. Dona recognizes that he does not fit the description of the worthy sorts of Brahmins and he is so impressed with Gotama's subtlty and knowledge that he is converted.
Another wonderful example of Gotama's skill as a teacher.
A very interesting fact revealed in this sutta is that the seer's of old mentioned by Gotama were apparently fully cognizant of all four jhaanas in precisely the terms found in the suttas.
There is also found in this sutta two statements which will strike the modern reader as belief in superstition: The statement that having intercourse with a pregnant woman will 'foul' the child; and having intercourse with a woman giving suck will in some way mess up the milk.
In order to cut off the knee-jerk reaction likly on the part of some: read carefully: these statements are not of Gotama's beliefs, but of the seer's of old and the Brahmins of Gotama's time. On the other hand this would be no easy thing to prove one way or the other, and the fact these beliefs are now held to be false seems to me to be just as doubtful a position as to hold that they are true. Put yourself in the place of the child in the womb of a couple engaging in intercourse - does it not seem reasonable that the flood of chemicals released in the body of a woman having intercourse would likely change the chemical composition of the milk? Of course the one view serves those greatly attached to indulging in sense-pleasures and the other serves to help control that appetite, but I suppose that had nothing to do with the change in point of view.