As the Buddha said on the SN 48.44: Pubbakotthaka Sutta
Those who have not known, seen, penetrated, realized, or attained it by means of discernment would have to take it on conviction in others that the faculty of conviction... persistence... mindfulness... concentration... discernment, when developed & pursued, gains a footing in the Deathless, has the Deathless as its goal & consummation; whereas those who have known, seen, penetrated, realized, & attained it by means of discernment would have no doubt or uncertainty that the faculty of conviction... persistence... mindfulness... concentration... discernment, when developed & pursued, gains a footing in the Deathless, has the Deathless as its goal & consummation.
And on the SN 50.1:
There are these five strengths. Which five? Strength of conviction, strength of persistence, strength of mindfulness, strength of concentration, & strength of discernment. These are the five strengths.
Just as the River Ganges flows to the east, slopes to the east, inclines to the east, in the same way when a monk develops & pursues the five strengths, he flows to Unbinding, slopes to Unbinding, inclines to Unbinding.
Confidence on the Triple Gem as a factor for stream entry on SN 55.1 Raja Sutta
"And even though a disciple of the noble ones lives off lumps of alms food and wears rag-robes, still — because he is endowed with four qualities — he is freed from hell, freed from the animal womb, freed from the realm of hungry shades, freed from the plane of deprivation, the bad destinations, the lower realms.
"And what are the four? There is the case where the disciple of the noble ones is endowed with verified confidence in the Awakened One: 'Indeed, the Blessed One is worthy and rightly self-awakened, consummate in knowledge & conduct, well-gone, an expert with regard to the world, unexcelled as a trainer for those people fit to be tamed, the Teacher of divine & human beings, awakened, blessed.'
"He/she is endowed with verified confidence in the Dhamma: 'The Dhamma is well-expounded by the Blessed One, to be seen here & now, timeless, inviting verification, pertinent, to be realized by the wise for themselves.'
"He/she is endowed with verified confidence in the Sangha: 'The Sangha of the Blessed One's disciples who have practiced well...who have practiced straight-forwardly...who have practiced methodically...who have practiced masterfully — in other words, the four types of noble disciples when taken as pairs, the eight when taken as individual types1 — they are the Sangha of the Blessed One's disciples: worthy of gifts, worthy of hospitality, worthy of offerings, worthy of respect, the incomparable field of merit for the world.'
"He/she is endowed with virtues that are appealing to the noble ones: untorn, unbroken, unspotted, unsplattered, liberating, praised by the wise, untarnished, leading to concentration.
Not understanding Kamma and rebirth as wrong view MN 117 Maha-cattarisaka Sukka
"And how is right view the forerunner? One discerns wrong view as wrong view, and right view as right view. This is one's right view. And what is wrong view? 'There is nothing given, nothing offered, nothing sacrificed. There is no fruit or result of good or bad actions. There is no this world, no next world, no mother, no father, no spontaneously reborn beings; no priests or contemplatives who, faring rightly & practicing rightly, proclaim this world & the next after having directly known & realized it for themselves.' This is wrong view...
So I would say that to follow the eightfold path and attain its fruits, one must have confidence in the triple gem. More, only by understanding kamma and rebirth will Right View be fully developed. So calling myself a Buddhist implies, to me, that I trust the Buddha, the Dhamma, and the Sangha. Implying that I accept kamma and rebirth as truths to be discerned by this mind.