It's very difficult to let go of narrow materialistic assumptions. People clearly struggle with a lack of understanding of transcendental realities and why the source of those realities are important.

The other thing, and spiritually sensitive people will confirm, there is a detectable "voice" that is supernatural. Not everyone is capable of hearing that voice since it, in the view of many, doing so depends on a functioning pineal gland.

As to the voice itself, I will assert that there's a hierarchy within the voice (in other words, it is multiple voices), and the highest one is God. That one voice is called the Word and is synonymous with love (why the understanding the transcedentals is so critical).

I don't expect an agnostic to understand this, but millions of people throughout history have with no difficulty.