No doubt you've heard someone say, "I'm spiritual but not religious" or similarly, "I don't believe in organized religion." Maybe even a friend or family member told you this. But what do these statements even mean? Or what about the so-called "Nones," people who claim no particular religious affiliation? Polling data suggests that over 1/4 of the US population fall into that category. This Pew Research Center survey found that many of these nones don't like the church's stand on social issues or don't like religious organizations in general.
What is at the heart of such convictions? It's pretty simple. The human heart wants what the human heart wants and doesn't want to be told what is right and wrong. "Religions" always have a set of doctrines, of beliefs, a worldview that shapes how that religion thinks about God, and mankind, and the afterlife. To be "spiritual but not religious" means recognizing that there is something outside of or greater than one's self, but not wanting to be subject to it, not wanting to be bound by certain doctrines or ways of thinking. In short, it means believing whatever one wants to believe, letting one's own heart determine truth, and good, and evil. It is a prideful mindset as old as the fall into sin itself.
The prophet Ezekiel experienced this. There were many false prophets spreading their lies during Ezekiel's time. They were all "spiritual but not religious." The Lord says to Ezekiel, "Prophesy against the prophets of Israel, who are prophesying, and say to those who prophesy from their own hearts: ‘Hear the word of the LORD!’ Thus says the Lord GOD, Woe to the foolish prophets who follow their own spirit, and have seen nothing!" (Ezek. 13:2-3). These false prophets spoke from their own hearts and from their own spirits, and not from God's Spirit.
Christianity has God's revealed word in the Scripture to lead our thoughts, words, and actions in this life and to prepare us for the life to come. God is real. He is personal. Sin is real, and it kills, and it separates us from God. God Himself provides the solution to this insurmountable problem, by providing His Son to atone for sin. Faith in the promises of Jesus saves us
So how do we witness to the nones? Start with prayer, and know that it takes time, and as you speak God's word to people it accomplishes the purpose for which He sends it.
Lutheran witness has some great articles on this spiritual but not religious phenomenon, from 2011, 2012, and 2022. Also check out this video.