Question

state any one basis for India to be a secular state

Answer 1

Well, first of all, India would be a secular country, not state.

And it could be a secular country as people of different religions, castes, creeds, ancestry lines live in the same place. And we accept that and try to live in peace and harmony, unitedly without any fights.

Answer 2

it enables people of different religion to live in harmony with other faiths.