Materialism

We may claim that denying the afterlife is scientific, but in fact it merely indicates a belief in materialism. The rishis believed that knowledge wasn't external to the knower but woven inside consciousness. Thus they had no need for an external God to solve the riddle of life and death. The rishis had themselves instead, which is very fortunate, because so do we. Each person is conscious. Each person has a self. Each person is certain of existence, that is, of being alive. With these raw ingredients, anyone can come up with firsthand knowledge of anything, no matter how deep the mystery appears.

Then why haven't we? Perhaps it's because we don't contact the deepest part of ourselves, which the rishis call Atman. The closest equivalent word in English is "soul."  The biggest difference between them is that in Vedanta, the soul isn't separate from God. Unlike the Christian soul, Atman cannot come from God or return to God. There is unity between the human and the divine; awareness of this unity is the necessary step that makes reality dawn.