Buddha often likened himself to a doctor, offering a treatment for the sufferings of the heart. He could not directly show newcomers the state of health - the state of nirvana - but if they followed his teaching, they could see it for themselves. The first indications that he was awakened - and that awakening was a good thing - came with "entering the stream" [sotapanna].
He also presented a few pragmatic arguments. A pragmatic argument focuses not on facts but on conduct. Buddha's main pragmatic argument is that if one accepted his teachings, one would be likely to pay careful attention to one's actions, so as to do no harm. When applied to the issue of rebirth and karmic results, through practicing his key teachings one leads a decent life in the here-and-now.
A jolly good life has its growing rewards, such as satisfaction and joys of doing good. And further, should the afterlife and karmic results not exist, a decent life and doing good would be nothing to regret. - T.K-
Those who go for a decent, progressive life, have made a lucky throw, holds Buddha. They do not degenerate.
I have heard that once when Buddha was on a wandering tour among the Kosalans with a large community of monks, he arrived at the brahmin village called Sala. The brahmin householders of Sala went to him, bowed down to him, and sat down around him. As they were sitting there, Buddha asked them, "Householders, is there any teacher agreeable to you, in whom you have found grounded conviction?"
"No, sir, not one."
"Then you should adopt and practice this safe-bet teaching, for when it is accepted and adopted, it should be to your long-term welfare and happiness," said Buddha.
"And what is the safe-bet teaching?" they asked him.
Then he told them. The argument: If bad actions lead to derangements here and worse conditions in the after-life and future lives, it pays to shun them. And if good actions lead to blessings in time, some even in this life, and others in the after-life and lives to come, it pays to incorporate them in one's daily life on an even keel. That is roughly his key teachings.
He went on to say, "Householders, there are four types of individuals in the world.
He (or she) who is on the right way, abstains from the taking of life. He abandons taking of what is not given, lives not by stealth but by means of a self that has become pure.
He abstains from divisive speech. He loves concord, delights in concord, enjoys concord, and speaks things that create concord.
He speaks words that go to the heart, that are polite and as appealing as should be.
He abstains from idle chatter. He speaks what is factual, what is in accordance with the goal. He speaks words worth treasuring, seasonable, reasonable.
He abstains from damaging seed and plant life.
He abstains from accepting male and female slaves.
He abstains from running messages.
He abstains from mutilating, executing, imprisoning, highway robbery, plunder, and violence.
He is inwardly sensitive to the pleasure of being blameless [sensitive versus the conscience].
He keeps OK control over his senses, inwardly sensitive to the pleasure of being blameless.
He acts with alertness.
[He or she takes up the good meditation practices, for great parts of the Gentle Middle Path presuppose it, and good progress depends on it.]
He seeks out a secluded place to live and brings mindfulness to the fore [trains himself to that end too].
He cleanses his mind of covetousness [by dhyana, meditation].
He cleanses his mind of ill will and anger [by deep meditation].
His mind gets inwardly stilled [by proficent meditation].
He enters and remains in the first dhyana [deep meditation. In Pali: jhana], rapture and pleasure [so he delights well].
"Then, with the stilling of thoughts and evaluations, he enters and remains in the second dhyana: rapture and pleasure born of well unified awareness free from the thoughts and evaluations of the first dhyana, with internal assurance.
Then, with the fading of rapture, he remains equanimous, mindful, and alert, and senses pleasure with the body. He enters and remains in the third dhyana, that is "equanimous and mindful, a pleasant abiding."
Then, loftier still, he enters and remains in the fourth dhyana: purity of equanimity and mindfulness.
While his mind is thus unified, he may incline it to [such as] knowledge of the recollection of past lives (lit: previous homes). He recollects his manifold past lives in their modes and details. This is a fruitful form of striving in deep dhyana. *
These teachings correspond to how to cultivate similar powers through samyana (focused awareness in deep meditation) in Patanjali's Yoga Sutras, book 3, v 4, 16 ff.
He sees - by means of the purified third eye - beings passing away and reappearing in accordance with their karma. He sees for himself how beings who were endowed with good conduct of body, speech, and mind, who did not revile the spiritual-noble ones, who held right views and undertook actions under the influence of right views - with the break-up of the body, after death, have reappeared in the heavenly world. He also sees beings passing away and reappearing.
"With his mind thus steadied, he discerns what is dukka (stress, suffering) and its causes and how to solve it by hindering its concomitant mental fermentations from growing.
With release, there is the knowledge: "Released. Task done."
This well accomplished one is called an individual who neither torments nor tortures himself nor others. He dwells in the here-and-now, sensitive to happiness.
When Buddha had finished his discourse, the brahmin householders of Sala said, "Magnificent, Dharma [the teaching and proper conduct in life] is made clear."
Adapted from MN 60 Apannaka Sutta, "A Safe Bet", translated from the Pali by Thanissaro Bhikkhu.