Question
When did Hinduism begin?
Answer
In ancient period, Hinduism was known as "Sanatana Dharma".
Sanatana Dharma is by its very essence a term that is devoid of sectarian leanings or ideological divisions. This is evident by the very term itself. The two words, "Sanatana Dharma", come from the ancient Sanskrit language. 'Sanatana' is a Sanskrit word that denotes that which which is Anadi (beginningless), Anantha (endless) and does not cease to be, that which is eternal and everlasting. With its rich connotations, Dharma is not translatable to any other language. Dharma is from dhri, meaning to hold together, to sustain. Its approximate meaning is "Natural Law," or those principles of reality which are inherent in the very nature and design of the universe. Thus the term Sanatana Dharma can be roughly translated to mean 'the natural, ancient and eternal way.' [Source: veda.wikidot.com/sanatana-dharma]
So, the simple answer is Hinduism was actually not a religion but a common practice which was being followed by our ancestors. So there is no question of a starting point for Hinduism or Sanatana Dharma.
Other references:
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