WE know nothing until we experience it. Until then, we can believe in something, which means we think its possible and so we try it and if one day we experience what we believed, then we know its true. Until then, there is no way of knowing.
Rahu 9th house is also its Maran Karaka sthana (MKS), which implies the planet feels like dying in this house because the energies are opposite to its nature. The belief is that, in past, the person cheated guru and got cursed by Guru.
In traditional times or even now in Indian culture, Rahu is often seen as the bad thing, Maya, cheating, etc. The person might change religion which is considered bad in traditional cultures.
Sometimes, this axis, makes a person very good business person who pretends to be a spiritual person externally. Fake it until you make it. So, the person wants to be spiritual but sometimes the old habits of making money at cost of others, lying, gossiping, false marketing, false smiles, lack of integrity, etc might be still there.
In my personal experience, the individual with this position, can be a beautiful and happy soul just like other positions. I have a friend with this position and she follows her traditional religion, respects her teachers and very deep into learning all the books, concepts, rules of religion.
All the Rahu in water signs seems to be pointing towards achieving emotional security.
what about ketu in the 9th?
As much as I have tried to meditate and connect to a spiritual path, I find that it is all taking place in the mind rather than my heart. So I finally came to the conclusion, that only faith is going to save me and to keep on walking on the path even when doubts and frustrations arise.