JBM,

You wrote:

"Spiritual things can only be discerned by the spirit"

This is what I was taught and accepted as reasonable as a Mormon. I now consider it a cop-out and circular reasoning. Essentially the unscientific theists are saying:

You scientists can't disprove the idea I or someone else invented about "supernatural things" using instruments and ideas based on natural laws because it would require you to accept and use the supernatural "spirit" to study those things!

The weakness of this argument is that it's circular. Where's the evidence there's a spirit or spiritual things? There's none, really.

If by "spiritual things" you mean appreciation for beauty, art, or other similar concepts, then atheists know them at least as well as theists do.