I was perusing the latest Banner of Truth magazine and noticed an article by Isaac Watts, entitled Rules for a Preacher's Conduct. (Impressive to still be being reprinted in periodicals 260 years after your death.)
He uses the term experimental religion and experimental preaching several times throughout the article. (He's not talking about wearing sandals, meeting in coffee houses and having "conversations" about what we think Christianity ought to be all about). He means Christianity that affects the way we live (ie. we are the subjects of the experiment, not Christianity). A form of religion that goes beyond mental assent to actually getting your feet wet. But not so much in the simplistic social justice sense that many modern (as in postmodern) Christians seem to, as in the experience of the interaction between the soul and the Holy Spirit and the conscience; the conflict between our proclivity to sin and desire for holiness. Or, in other words, the experiment is not in being good people so much as in being God's people, with an understanding of our need for God and the provision of the gospel, as the basis for change.
Trying to effect behavourial change (being good) without embracing foundational change (being God's) is like trying to drive a car without an engine. Seems to me we need more experimental religion.
I was attempting to distinguish between Pick'n'mix approach to religion (ie. I define value) where we take the bits that we like (e.g. caring for the poor, charitable giving, particular liturgical forms etc) and humble orthodoxy (ie. God defines value) in which we take the whole gospel, as revealed. In the former case, we are doubting God more than we doubt ourselves, in the latter we doubt ourselves more than we doubt God.
Watts' experimental religion centres on what Paul describes as "work[ing] out your own salvation with fear and trembling for it is God who works in you, both to will and to work for his good pleasure."