The zealots, it seems, have run amok. A Terence Corcoran column last week warned ''proponents of free markets,'' that fanatical sect, have ''run off the rails'' with their latest idea: charging drivers to use city roads, as a means of reducing congestion.

Corcoran, if I recall rightly, at one time would himself have been numbered among that church, but now seems to have lost his way. Indeed, this filthy apostate spends the entire column blaspheming and insulting the faith of his fathers. I therefore call upon all good price system zealots to kill him.

No, cancel that, I forgive him. Our troubled brother is rather in need of serene spiritual counsel. It's not immediately clear why the idea of pricing roads should be any more disturbing than pricing pork, except that it hasn't been tried before.

Or rather, it has been tried, but only in strange foreign places like Singapore. It might seem material to inquire whether the system has worked in Singapore. As it happens, it has. This practical success is perhaps what Terry means by the concept's ''vague theoretical attraction.'' One can't be sure.

It doesn't matter, anyway, because: ''Road pricing will not work.'' This devastatingly simple argument, about which more later, masks a more complex underlying theory: people like sitting in traffic jams. I'm not making this up. ''The more congested a city becomes,'' Terry has discovered, ''the more people want to live there.''

GULPING SMOG

There it is. People want to live in Toronto not for the pleasant neighborhoods, the lake, the night life, or to be near their place of work, but for the exquisite hours spent in suspended automation between these delights. What's a glass of white wine in a cozy jazz bar compared with two hours gulping smog on the Don Valley Parkway?

So insistent are they on this pleasure that no price, no matter how high, will deter them. The ''urge to urbanize'' is ''beyond price control.'' After all, Terry says, look at housing. The price of real estate in downtown Toronto has soared, yet this ''has not deterred anybody from building and living and working in downtown Toronto.'' Really? It hasn't deterred anybody? How does he know?

This will indeed be news to those forced out into surrounding communities by the high cost of living downtown. Perhaps their urge to urbanize is inadequate. Or perhaps the housing market is working as it should. We see land prices skyrocketing; we do not see people backed up for blocks to buy a house. Housing is an example of a market with defined property rights and no important external costs. If I buy a house, my use of it does not normally impose costs on my neighbors, or prevent them from enjoying their own homes. By contrast, my use of a road does impose costs on other drivers by impeding their passage.

The result is to reserve road space for those who need it least: the drivers for whom time is no concern. Those in a hurry have no choice but to wait with the slowpokes, or to walk. Pricing road use forces drivers to take into account the costs of congestion, and allows them to express the intensity of their demand. (Another solution is to subsidize the competition: public transit.)

Ah, but remember: road pricing will not work. For one thing, Terry protests, we already pay a price for driving - parking, insurance, gas taxes - without visible effect. Oh dear. The poor fellow seems no longer to recognize the difference between the total cost of driving a car, and the marginal cost of using a particular road at a particular time.

We are nowhere near to having too little road space in total; the problem is bottlenecks at peak periods on certain main thoroughfares. Raise the price on overused roads, and lower the price on underused, and the traffic jam suddenly is no longer the unavoidable fact of life experience might suggest.

But how much is the proper amount of traffic? And who decides? Simple: drivers. They have their choice of routes. They select the combination of price and traffic conditions that best suits them. Efficient pricing would be best achieved by assigning each street to private owners, but I have no doubt a public utility could manage nearly as well.

One is left still wondering what could possibly have put Terry in such a fury. The last paragraph is revelation. ''The only significant effect of road pricing,'' he says, ''would be to provide governments with another source of revenue and add another cost to business.'' See? It's a tax. And not only that, a tax on business. Free market zealots, indeed: Terry's just being plus royaliste que le roi.