Why do babies so easily learn to swipe an iPhone? They’re not simply mimicking us. Tertullian would say they’re pointing us back to the hinge of salvation.
Hand a baby an iPhone. Early on, they learn to swipe across the face of the phone, most often using their index finger. You might assume they’re imitating adults (they are to some degree). But running our fingertips sideways across an object gives us a surge in neural voltage as well as sensual pleasure.
That’s because at the center of our fingers are concentric ridges and grooves. We instinctively move our fingers over an object roughly perpendicular to these ridges, allowing friction to tug on each ridge. The changes in pressure produce changes in voltage in our neural system, which releases oxytocin, a pleasure chemical.
This central part of your fingertip contains the finest, densest set of ridges. That’s where we first make contact with an object. As we move toward our palm, the ridges become progressively wider. The nerve endings are most dense, so we lay our palms lay flat on an object. In this way, we touch the largest possible surface.
This is how the Bible describes knowledge. It’s how Adam came to know Eve so that she bore a child (Gen.4:1). But if you’re squeamish about sexuality, I’d urge you to read no further. I’m going to describe going from fingers to flesh to faith.
According to physiological and behavioral evidence, the left pars opercularis, the area of the frontal lobe critical for speech production, is most closely linked to nerves located in the stretch of skin between your thumb and forefinger. Language is most naturally formed by touching—especially with our fingertips. When Adam met Eve, he coined words like “bone” and “flesh.” Since there were no dictionaries at that time, where did Adam come up with those words? By touching Eve.
Assuming Adam was like most men, he started with fingers on Eve’s breasts but then moved to palm laying flat, presenting the largest possible surface for contact. Adam was instinctively following the pressure ridges that release oxytocin.
Together, the couple next moved toward a massive dump of oxytocin. There are slower nerve endings on the rest of the body, particularly on our lips, nipples, and genitals. The clitoris is enmeshed in these sensory neurons. While oxytocin is increased by massage, kiss, or hugs, it’s massively dumped into our neural system at the moment of sexual consummation, making sex so pleasurable. This is what Adam and Eve experienced.
This is one way we “taste” salvation. Tertullian (160–225), “the father of Western theology” rightly taught that “the flesh is the hinge of salvation” (Caro salutis est cardo). We “pivot” toward the spiritual life through our flesh, mostly by taking and eating (the Eucharist), but also in sexual consummation. The progression begins with our fingers, moves to our hands and lips, and finds its deepest expression in nuptial consummation (for married couples). Our brain then puts to words what our flesh has felt.
My sense is this is what religious “nones” and exiles feel is missing in the modern church. It’s high tech. But it’s not high touch. They feel what Walt Whitman wrote, “Your facts are useful, and yet they are not my dwelling.” It turns out we dwell mostly in what we physically touch. Churches that see our flesh and sexuality as “the hinge of salvation” will be more likely to help today’s spiritual seekers. They don’t have to start with sex. Simply start with a baby swiping an iPhone.
 Tertullian, De resurrectione carnis (Treatise on the Resurrection), 8, 2.