But I don’t speak about such things … You are right that the term Buddhist should be defined, before discussing it. As I said Kalama Sutta is directed to outsiders who are without teacher and are quite disoriented, since various teachers teach various things.
So with background of Kalama Sutta, Buddhist may mean “anyone who already recognised the Buddha as his teacher, or at least has some hopes that Dhamma may improve his existential situation.”
Lord Buddha quite clearly described what is at stake when comes to rebirth and law of action:
“Since there actually is another world, one who holds the view ‘there is no other world’ has wrong view. Since there actually is another world, one who intends ‘there is no other world’ has wrong intention. Since there actually is another world, one who makes the statement ‘there is no other world’ has wrong speech. Since there actually is another world, one who says ‘there is no other world’ is opposed to those arahants who know the other world. Since there actually is another world, one who convinces another ‘there is no other world’ convinces him to accept an untrue Dhamma; and because he convinces another to accept an untrue Dhamma, he praises himself and disparages others. Thus any pure virtue that he formerly had is abandoned and corrupt conduct is substituted.623 And this wrong view, wrong intention, wrong speech, opposition to noble ones, convincing another to accept an untrue Dhamma, and self-praise and disparagement of others—these several evil unwholesome states thus come into being with wrong view as their condition. (…)
“Since there actually is doing, one who holds the view ‘there is no doing’ has wrong view. Since there actually is doing, one who intends ‘there is no doing’ has wrong intention. Since there actually is doing, one who makes the statement ‘there is no doing’ has wrong speech. Since there actually is doing, one who says ‘there is no doing’ is opposed to those arahants who hold the doctrine that there is doing. Since there actually is doing, one who convinces another ‘there is no doing’ convinces him to accept an untrue Dhamma; and because he convinces another to accept an untrue Dhamma, he praises himself and disparages others. Thus any pure virtue that he formerly had is abandoned and corrupt conduct is substituted. [406] And this wrong view, wrong intention, wrong speech, opposition to noble ones, convincing another to accept an untrue Dhamma, and self-praise and disparagement of others—these several evil unwholesome states thus come into being with wrong view as their condition.
MN 60
Of course since we merely believe that Lord Buddha was the Buddha, He may be quite wrong and there is no such thing as rebirth and law of action, if one is clever enough not to be caught by police and psychopathic enough not to feel any remorse, one can do everything.
But if Buddha was really Buddha, the reason why one will faced negative consequences are clearly stated by the Sutta.
But again it may not be anything really unpleasant … apart one really horrible thing: one’s own connections with Dhamma will untighten, and another opportunity to meet Dhamma may not happen soon.
Even in much less important areas to undermine teacher words is consider as not proper attitude, so what about Dhamma?
Do notice that atheism in fact undermines holy life:
“Sandaka, these four ways that negate the living of the holy life have been declared by the Blessed One who knows and sees, accomplished and fully enlightened, and also these four kinds of holy life without consolation have been declared, wherein a wise man certainly would not live the holy life, or if he should live it, would not attain the true way, the Dhamma that is wholesome.” (…)
Here, Sandaka, some teacher holds such a doctrine and view as this: ‘There is nothing given, nothing offered, nothing sacrificed; no fruit or result of good and bad actions; no this world, no other world; no mother, no father; no beings who are reborn spontaneously; no good and virtuous recluses and brahmins in the world who have themselves realised by direct knowledge and declare this world and the other world. A person consists of the four great elements. When he dies, earth returns and goes back to the body of earth, water returns and goes back to the body of water, fire returns and goes back to the body of fire, air returns and goes back to the body of air; the faculties pass over to space. [Four] men with the bier as fifth carry away the corpse. The funeral orations last as far as the charnel ground; the bones whiten; burnt offerings end with ashes. Giving is a doctrine of fools. When anyone asserts the doctrine that there is [giving and the like], it is empty, false prattle. Fools and the wise are alike cut off and annihilated with the dissolution of the body; after death they do not exist.’
“About this a wise man considers thus: ‘This good teacher holds this doctrine and view: “There is nothing given…after death they do not exist.” If this good teacher’s words are true, then both of us are exactly equal here, we stand on the same level: I who have not practised [this teaching] here and he who has practised it; I who have not lived [the holy life] here and he who has lived it.
Yet I do not say that both of us are cut off and annihilated with the dissolution of the body, that after death we shall not exist. But it is superfluous for this good teacher to go about naked, to be shaven, to exert himself in the squatting posture, and to pull out his hair and beard, since I, who live in a house crowded with children, who use Benares sandalwood, who wear garlands, scents, and unguents, and accept gold and silver, shall reap exactly the same destination, the same future course, as this good teacher. What do I know and see that I should lead the holy life under this teacher?’ So when he finds that this way negates the living of the holy life, he turns away from it and leaves it.
“This is the first way that negates the living of the holy life that has been declared by the Blessed One who knows and sees, accomplished and fully enlightened, wherein a wise man certainly would not live the holy life, [516] or if he should live it, would not attain the true way, the Dhamma that is wholesome.
“Again, Sandaka, here some teacher holds such a doctrine and view as this: ‘When one acts or makes others act, when one mutilates or makes others mutilate, when one tortures or makes others inflict torture, when one inflicts sorrow or makes others inflict sorrow, when one oppresses or makes others inflict oppression, when one intimidates or makes others inflict intimidation, when one kills living beings, takes what is not given, breaks into houses, plunders wealth, commits burglary, ambushes highways, seduces another’s wife, utters falsehood—no evil is done by the doer. If, with a razor-rimmed wheel, one were to make the living beings on this earth into one mass of flesh, into one heap of flesh, because of this there would be no evil and no outcome of evil. If one were to go along the south bank of the Ganges killing and slaughtering, mutilating and making others mutilate, torturing and making others inflict torture, because of this there would be no evil and no outcome of evil. If one were to go along the north bank of the Ganges giving gifts and making others give gifts, making offerings and making others make offerings, because of this there would be no merit and no outcome of merit. By giving, by taming oneself, by restraint, by speaking truth, there is no merit and no outcome of merit.’
“About this a wise man considers thus: ‘This good teacher holds this doctrine and view: “When one acts…there is no merit and no outcome of merit.” If this good teacher’s words are true, then both of us are exactly equal here, we stand on the same level: I who have not practised [this teaching] here and he who has practised it; I who have not lived [the holy life] here and he who has lived it. Yet I do not say that whatever both [of us] do, no evil is done. But it is superfluous for this good teacher…What do I know and see that I should lead the holy life under this teacher?’ So when he finds that this way negates the living of the holy life, he turns away from it and leaves it. MN 76
