Destruction is creative, to quote that amiable nihilist Bakunin, and right he was! This is especially true in a fully developed city like New York, where construction rarely occurs without annihilating what it replaces. Consider two projects planned on the Upper East Side of Manhattan: the re-renovation of the plaza in front of the General Motors building and the plans for a Whitney Museum expansion.

For sheer enjoyment, I urge you to visit the art galleries in the Squibb building at 57th and Fifth. Go especially to the Forum Gallery on the fourth floor, where you will find a fine exhibition by the realist painter Jane Lund. But while you are there, wander over to the window that looks out onto Edward Durell Stone’s GM Building. From this vantage point, you can see the wholesale destruction of the public plaza out front. Enjoy it.

You may remember that, for the first few years of the present millennium, this building belonged to Donald Trump. His first order of business, after applying his name in gold letters to the facade, was to destroy the sunken Astroturfed plaza that had been there since the building went up in 1968. In so doing, he placed the entire city in his debt.

But the result, though better than what it replaced, was not nearly good enough. There was an abundance of brass and marble that brought to mind the men’s room in the Trump Taj Mahal. Worse still was the way the site was clumsily set at shifting levels. And worst of all was a retail space that reared up in the very center of the site, blocking the pedestrians’ view of the building’s entrance.

As punishment for such a transgression, one of the more ill-considered in the history of commercial realty, this space failed to attract a single client in its five years of existence.

Now Macklowe Properties has acquired the site and engaged the prolific firm of Gensler Architects to do what it can. Even in a city as relentlessly changeful as New York, the fact that this space should be transformed again, after only five years, is nearly unprecedented.

Both the owners and the architects are holding their cards close to their vests. But I learned from one of the overseers of the project that the idea is to create a public space that recalls the plaza in front of the Seagram Building: a level, Minimalist space with two reflecting pools.

If that is indeed their intention, it is a very auspicious development. For the plaza in front of the GM Building turns out to be one of the most welcome public spaces in the city. That role will be only enhanced if things progress in the direction in which they seem to be going.

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Speaking of things I would not be sorry to erase from the urban fabric, the question has now been posed, yet again, whether the Whitney Museum should expand and, if so, whether it should do so at the expense of two row houses just south of the Marcel Breuer structure on Madison.

Not everything old is worth preserving, even Hopper-esque buildings like these, which date from the 19th century. After all, it is not as though we didn’t have 20,000 other row houses around town, many of them along Madison Avenue, just a stone’s through from the Museum.

And certainly the Breuer building was never a good fit for its present location, if indeed it could be said to fit into any other context, natural or manmade. To create a fairly uniform structure across the entire block would probably improve matters greatly.

To date, we have yet to see any but the most preliminary renderings of the planned expansion, designed by Renzo Piano and intended to double the size of the museum. Among the promised goodies are a 260-seat auditorium, a new entrance and enlarged lobby (which could hardly be worse than the Brutalist chamber that we see today), an outdoor sculpture gallery, and a real library.

All of that is very well. Still, it is regrettable that there is talk of building the annex as a 16-story tower, whose top seven stories would be residential. This probably makes excellent financial sense, but it will rule out any possibility that that the two structures can be fused into one greater whole.

Ironically, the blockish structure proposed, 20 years ago, by Michael Graves seemed likely to achieve this effect very well. The result would have been a building whose overall effect was more powerful than either Breuer’s or Mr. Graves’s contribution by itself.

Though Mr. Graves’s highly postmodern (that is, neoclassical) design was taken rather seriously at the time, the general feeling nowadays is that, by not building it, we dodged a bullet. But just as I was suspicious at the time of all the people who “knew” it was the right thing to do, so now I am suspicious of all those who “know” that it would have been the wrong thing.

What I object to is the going notion that it was a mistake, even if, at the time, we didn’t “see” that it was a mistake. Is it so far beyond the powers of introspection of the architectural community to conceive that the manifest “rightness” of Mr. Piano’s design is probably nothing more or less than the fact that he and we occupy this cultural moment, however brief it may be? This insidious mirage of self-evident “rightness” is the Waterloo of most architectural discourse, whether it is found in the humblest “man in the street” or in the tenured academic ex-cathedrating from his ivory tower.

It is far too early to say if anything good will come of Mr. Piano’s design, indeed, whether anything will ever be built at all. But were it to be built, the one consolation we must never deny ourselves is the proviso that, if we come to repent what we have done, we should have the option to tear it up and start all over.