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It's completely lacking dogma, doctrine, and the inflexibility which come with those spiritual vices. The Buddha himself said: Do not believe in anything (simply) because you have heard it; Do not believe in traditions, because they been handed down for many generations; Do not believe in anything, because it is spoken and rumored by many; Do not believe in anything simply because it is found written in your religious books; But after observation and analysis, when you find that anything agrees with reason and is conducive to the good and benefit of one and all, then accept it and live up to it.
Here's what modern Buddhist thinker, Dr. Ambedkar writes about this novel spiritual approach: “Buddha wanted his religion to remain evergreen and serviceable at all times. That is why he gave liberty to his followers to chip and chop as the necessities of the case required. No other religious teacher has shown such courage. They were afraid of permitting repair, because the liberty to repair may be used to demolish the structure they had reared. Buddha had no such fear. He was sure of his foundation. He knew that even the most violent iconoclast will not be able to destroy the core of his religion.”