In an earlier and, some will think, wiser time, conservatives were known for their supicion of untried theory. "We are not given to reckless experiment" was a commonly heard affirmation of the conservative faith. Now no longer. The Reagan adminstration has broken dramatically with that counsel. Supply-side economics, now fading into slightly snide memory--"Laffer sold us a bill of goods"--and single-minded, single-remedy monetarism were both untried, or largely untried, on the American scene. Neither, on being tried, has shown that the old caution was ill advised.

Now, although it isn't fully recognized, ther is another brand-new economic doctrine in Washington. It is the peristalsis theory. Conservatives who have observed the first two thrusts into the unknown and the consequences should now, at long last, be on the alert. Simply because an administration calls itself conservative doesn't mean that scholars and politicians who so describe themselves should remain silent, suppress hteir beliefs. For shame. And Democrats, boll weevils apart, should know that the administration economists are by way of providing them with yet more ammunition, albeit at considerable cost to their constituents and the country.

The peristalsis theory is in lineral descent from monetarism, and it derives not as a metaphor but by analogy from medicine and physiology. Monetarism--the attempt at rigorous control of the money supply by a tough restraint on bank lending and high interest rates--was meant to control inflation ion a ively painless way. A short period of readjustment, Milton Friedman and Beryl Sprinkel believed and often promised, and then prices would be stable and all would be well.

Instead, after the fashion of untried theories, it has had and is having exceedingly painful and, by its partisans, wholly unexpected consequences. The automobile industry, the thrift institutions as they are called, International Harvester, Pan Am and the other airlines, and the millions who either have been thrown out of work or, new on the job market, are unable to find employment are all taking a beating. Were liberal Democrats so to to single out busnessmen, mostly Republicans, for the punishment they are now getting from Republicans, they would never, never be forgiven. The effect of the great new monetary experiment is a very severe recession. So now enters the peristalsis theory.

It doesn't deny that monetary policy has had the effects just mentioned, although there is effort to hold that the economy, in its inherent cyclical way, moved itself into this recession. But the recession, it is argued, is a medicine that must be taken and suffered to get the poison out of the system. That poison is inflation; once it has been eliminated, it will be gone for good. a one-time remedy for a one-time disorder.

These last weeks have seen a whole raft of references to the peristalsis effect. The president has said repeatedly that there will be some very bad times ahead but they are the price of better days beyond. Othes in the administration have echoed his words. And Murray L. Weidenbaum, chairman of the Council of Economic Advisers, has been specific; the next quarter or two will be very bad; unemployment will reach 9 percent of the labor force. But the suffering, admittedly not by those predicting it will be wholly, if painfully, therapeutic. By next summer inflation will have been cured, the exonomy will be expanding, and for Republican representatives and senators up for re-election, an unspoken thought, the prospects will be terrific.

It's nonsense; one could extend the medical analogy to what it really is, but, in a family newspaper, that would not be nice. Given the tax reductions and the military spending, the economy could well recover next year. But with the big deficit that is in prospect, and the absence of any restraint on wages and corporate prices, inflatin will then resume. And given the new enthusiasm of the administration for deficit financing, another thing for conservatives to ponder, it will be faced with the choice between another round of murderously high interest rates preciitating another recession or of accepting more price increases, more inflation. The notion that inflation can be extruded once and for all by the present suffering is a triumph of analogy over intelligence. So, by next summer, the peristalsis theory will join supply-side economics and single-minded mnetarism, not perhaps in the ashcan of history but certainly in its septic tank.