So now we know: Ronald Reagan really does mean to upgrade U.S. relations with the government of Taiwan in a way certain to offend the Chinese government in Peking and threaten to upset the "normalization" of relations between mainland China and the United States.

And he means to make Jimmy Carter's treatment of Taiwan a campaign issue as well.

That much is clear in the 10-page, definitive, once-and-for-all statement of the Reagan China policy made public the other day. Prepared after consultation with running mate and China hand George Bush, there was nothing offhand about it and no room for the "misinterpretations" that Reagan aides have blamed for weeks of confusion over just what the Republican candidate really had in mind for China.

Still less could Reagan have had any questions about how it would be received in Peking. Having just been there, Bush knew how big a buzzword "official" is when it is applied to the nature of the American connection with Taiwan. As the official government radio had broadcast earlier, the idea that "the United States can establish official relations with Taiwan, while simultaneously maintaining its friendly relations with mainland China)$ . . . is utterly deceptive talk."

Reagan sees just the opposite deception. "You might ask what I would do differently," he said in his formal statement. His answer: "I would not pretend, as Carter does, that the relationship we now have with Taiwan, enacted by Congress, is not official." By way of rubbing it in, Reagan's statement uses the word "official" seven times in the course of describing the workings of last year's Taiwan Relations Act, which set up entirely unique machinery for conducting U.S. relations with Taiwan.

He has a point: there is some necessary ambiguity and no little subterfuge involved here. We are talking about the diplomatic bridging of an almost unbridgeable gap. Thus the U.S. instrument for dealing with Taiwan is undeniable weird. It is a District of Columbia corporation, created, financed and watched over by Congress, and staffed by government personnel on leave of absence and with full right of return to their government jobs.

So true enough, the American Institute of Taiwan does look, act, sound, smell "official." But when Reagan goes on to say that it is "hypocritical" to pretend that [it] is not something of an official relationship" and that he will have none of it, he is not unmasking hypocrisy or stripping away disingenuous double talk. He is striking at the essential element in the commitments and understandings that made "normalization" possible in the first place.

In the famous Shanghai communique at the time of Richard Nixon's opening visit to China in 1972, the ultimate resolution of the Taiwan question was fore-ordained with the explicit American abandonment of the "Two China" view: that all Chinese . . . maintain there is but one China and Taiwan is a part of China. The United States government does not challenge that position."

The next question in the normalization proces had to do whether the United States would come to recognize that the capital of this "one China" was in Peking, where the United States had a liaison office, or in Taiwan, where we had an embassy. The inevitable answer -- the only logical consequence of the Nixon initiative -- had to be the offer of full diplomatic recognition to Peking. There then remained the final question: whether to insist on maintaining something "official" in the way of a liaison office in Taiwan.

Reagan insists he would have held out successfully, for a liaison office -- although even he concedes that "that is behind us now." In any case, Carter found the Chinese adamant. And so the "normalization" agreement includes a joint communique, which states that "the people of the United States will maintain cultural, commercial and other unofficial relations with the people of Taiwan." A separate American statement speaks of "relations without official government representation."

To meet these commitments, the United States agreed to jerry-build something that both parties could choose to look upon as not being "official" -- and never mind the appearances. The issue, in short, is nicely joined. It is no longer worth wondering whether Reagan understands why there is much more here than, in his words a "transparency" or mere bypocrisy. He doesn't want to understand.

"The issue is not how I feel about Taiwan," he says. "The issue today is what Carter foreign policy is doing to our allies and to the United States' position in the world, and this is just another example of it."

That's one way of putting it. A better way is to ask whether it makes sense to put at risk this country's large geopolitical interests in the "normalization" of Chinese relations for the sake of nothing more than what Reagan himself describes as "petty practices of the Carter administration which are inappropriate and demeaning to our Chinese friends on Taiwan."