Full Idea
Zarathustra's achievement was for the first time to present a god who is an abstract concept - he broke with the tradition of a pantheon of gods.
Gist of Idea
Zarathustra was the first to present a god who is an abstract concept
Source
Zoroaster (The Gathas (seventeen hymns) [c.900 BCE]), quoted by Peter Watson - Ideas Ch.05
Book Reference
Watson,Peter: 'Ideas: from fire to Freud' [Phoenix 2006], p.153
A Reaction
The more abstract the gods become, the harder it is to challenge their existence.