With the beginning of the kamikaze missions we call denominational conventions only a month or two off, it is proper and wise to prepare ourselves for what will happen at most of them. Delegates will fight over authority and sex—defined respectively as ways of trying to govern denominations, and abortion and homosexuality.

One of my favorite metaphors for these assemblies, so easily overtaken by irrationality and the lack of common sense, is the family reunion. The attractions and repellings at church conventions match those emotionally charged encounters under the picnic trees. Relatives gorge and smile, gossip and backbite. But they come back for another round the next year.

Most denominational families get along pretty well during most of the year, doing the Lord’s work and coexisting in Christian community. It is always wondrously revealing to see their other selves surface at conventions, where traffic snarls, bumpers bump and road rage rages. What causes the jam-ups?

This second metaphorical explanation hit me as I read Stephen Budiansky on traffic, “The Physics of Gridlock,” in the December Atlantic Monthly. Americans think gridlock results from merging, entering and exiting traffic, or from “gaper blockings” at accident sites on superhighways, and the like. To improve things come experts who give obvious but only partially successful advice, like “add road space” and “lower the number of vehicles.” Then all will be well.

No, say the German theoretical physicists whom Budiansky cites. They claim that traffic behaves much like gas molecules encountering bottlenecks. But “the eeriest thing” the German equations suggested, Budiansky reports, “was the implication that traffic congestion can arise completely spontaneously under certain circumstances.” Traffic can flow at a density a road should be able to handle “and then suddenly gel into a slow-moving ooze.” And a traffic jam lasts long after any occasion for it has passed. The phenomenon is called hysteresis—and denominations will suffer it during convention season.

Some Americans resist this German model “because of its assault on rational determinism and common sense.” But, I ask you, look around and ahead of and behind you when next you are caught in a traffic bottleneck on an expressway and try to account for the snarl commonsensically and rationally.

Think of the topics that tore denominational assemblies apart 30, 20 or 10 years ago: can you account for them rationally? And do we now really think that the votes church bodies cast on questions such as the ordination of homosexuals or the forbidding of the blessing of gay unions will settle much of anything? Can you remember when last you heard of a layperson, gay or straight, united or solitary, being excommunicated? The only authority modern religious bodies have is over who gets admitted to and remains in the clergy ranks. Convening denominations spend their time on clerical traffic control.

And all the while the laypeople move along, sometimes in free flow and sometimes caught in bottlenecks, sometimes spontaneously doing the works of the Lord and sometimes spontaneously jammed and prevented from doing it by—what? By what gets resolved or unresolved at the church conventions? Maybe the gridlocks have more to do with spontaneous hysteresis, not to be overcome by human parliamentary procedure but only by the power of the Holy Spirit, who comes and goes as spontaneously as the wind.