ONE OF THE GREAT canards of American politics is that liberals are dreamy and somewhat soft in both the heart and the head, while conservatives are pragmatic -- people moved by neither ideology nor romance, but only by results. We have before us the Reagan administration to prove that this is not the case at all.

In both domestic and foreign policy, the administration seems, in the fashion of the true liberal, to have constructed a theory and then gone off to see if it works. On the home front, we have the propagation of a theory of economics that holds that what is more important than results is the appearance of results. And overseas, we have a secretary of state dashing around the Middle East telling Arab governments that their enemy is not, as they always thought, Israel, but Soviet expansionism. In theory, they should believe him.

The trouble with Alexander Haig's theory is that is it just that: theory. It may be true that Soviet expansionism represents the real threat to Saudi Arabia and Israel does not. To the extent that Israelis are unlikely to occupy Mecca in the near future, this is true. But the theory ignores the fact that Saudi Arabia and other Arab states have fought six wars with Israel, not with Russia. It is Israel, not Russia, that has been the target of the Arab propaganda effort, and the refugees who so complicate the Middle Eastern situation are from Palestine, not from the Ukraine.

To ask the Saudis and the Jordanians to turn their back on all that, to accept some geopolitical theory of big-power rivalry that makes a lot of sense in the situation room at the White House but not in any coffee shop in Beirut, is asking a bit too much. And to ask it in advance, as Haig did, to set out his wonderful plan publicly, gave both the Saudis and the Jordanians no choice but to shake their heads and say, "No, no. We know who our enemy is." Scratch one wonderful theory.

On the domestic front, there is similar nonsense. Here, the theory is that inflation is a product of the expectation of inflation -- that after a decade of prices going up, people expect prices to go up and so they do. Thus, this theory says that what the government has to do is get people to expect that inflation will decrease. Since it is psychology that produced inflation, it is psychology that will bring it down.

The trouble with this theory is that inflation occurred without anyone expecting it and it continued even though for a long time it was seen as the exception and not the rule. This does not matter to the theorists who think that once you convince people you are serious about ending inflation it will end. To this end, you cut the federal budget, play tough with deficits and act mean with a buck even though all this does not, in any direct way, have much to do with the rate of inflation. No matter. It is the psychology of if all that matters -- the noise.

But the people aren't listening. The latest Washington Post/ABC News poll shows the people more pessimistic about the Reagan administration bringing inflation under control than they were one month earlier. They feel this way even though the administration has cut the bejesus out of the budget and its programs have, until recently, all but sailed through Congress. Nevertheless, the public does not seem to be "hearing" the noise and is instead looking at the math. Things are more expensive than they used to be.

It will be interesting to see if the administration adapts its programs as it goes alaong, if it goes for results or prefers to adhere to a plan just because it is theoretically pure -- if, say, it is more interested in bringing inflation under control or knocking the stuffings out of the New Deal, in dealing with the problems of the world or proving that Russia is a godless, heartless kingdom ruled by the devil.

In the meantime, a cruel, cynical person could point out that there might be something wrong with these theories -- that the administration is not dealing with the world as it is, but as they think ti should be. We all know, though, that this could not happen. It is conservatives who are pragmatic and liberals who are dreamers.

That's the theory, anyway.