Parsi and Irani Zoroastrians characteristically affirm that the community is closed, that Zoroastrian identity passes by birth to the children of Zoroastrian parents, and that conversion and, in the stricter view, marriage outside the community are not accepted. On this understanding one is born a Zoroastrian rather than becoming one, and the faith is preserved within the descent group. The position is bound up with the small community's long experience as a minority and with its concern to maintain religious and, for many, ethnic continuity.
The community's closed character is bound up with its own founding narrative: the Qissa-i Sanjan, a sixteenth-century Persian-language account of much earlier events, describes Zoroastrian refugees fleeing the Arab Muslim conquest of Persia and arriving by sea on the coast of Gujarat, where the local ruler is said to have granted them refuge on condition that they adopt local language and dress while retaining their own religion, a story often illustrated by the image of sugar dissolved into a full cup of milk, sweetening it without causing it to overflow. Historians treat the text's precise dating and details as legendary rather than a strict historical record, but the Parsi community has long drawn on the story to explain both its integration into Indian society and its determination to preserve religious boundaries around that integration.