If Apple weren’t so orderly, disciplined, and predictably well run, you could almost call it schizophrenic. On the one hand, it’s the world’s most successful mobile technology company—the firm that sparked the smartphone and tablet boom, and the only one that’s reaping any significant profits from these new devices. Apple, more than any other company, is banking on what it calls the “post-PC” era, an age in which we get most of our stuff done on small, Internet-connected portable machines, not the hulking desktops and notebooks that now clutter our lives. Note that at its developer conference on Monday, most of Apple’s innovations were reserved for its mobile operating system. While it did announce several new features for a new version of the Mac OS, many of them—as Wired’s Steven Levy points out—were imports first invented for Apple’s phones and tablets.

But it’s too simple to say that Apple is giving up on PCs. Look at its amazing new laptop, which—clunkily and confusingly—is called the MacBook Pro with Retina display. That name suggests the new machine is closely related to Apple’s current line of MacBook Pros, which are stylish but pedestrian, old-fashioned laptops. The Retina MacBook’s real sire is actually the MacBook Air, the tiny machine that the company first launched in 2008. Over the last four years, Apple has transformed the MacBook Air from an expensive and underpowered novelty line into the best group of notebooks on the market. The Air—and now the similarly thin and light and flash-storage-having Retina MacBook Pro—represents the future of personal computing, while the standard MacBook Pro and the other computers in its class feel like pre-post-PC machines, devices that are hopelessly stuck in the past.

And that’s what I mean by schizophrenic: At the same time that it is killing the PC, Apple keeps extending the life of the personal computer with notebooks like the Air. That the same company is doing both these things is quite strange and spectacular—imagine if, in addition to building the Model-T, Henry Ford was also working on a way to breed faster, less smelly horses.

Apple isn’t really at war with itself, because in many ways the Air is a complement to the iPad, not its enemy. Well, that’s the case today, anyway. At some point the two machines will have to collide—either the Air or the iPad will win out, or we’ll see some novel combination of the two. Whatever happens, this much is clear now: If the once mighty personal computer is to have any future, the MacBook Air is its last best hope.

I first dove into the Air in 2010, when Apple released the 11-inch model for $999, a price I found irresistible. When Apple updated its Airs with faster processors last year, I traded in my 11-inch model for the 13-inch. I found both to be exceptional machines, the best portable computers I’d ever used. The Air does everything I can do on a standard laptop, but it has the size, weight, and battery life that’s more in line with a tablet. It’s also quieter than a standard laptop—it doesn’t have any spinning drives, and its temperature fan only kicks in when I watch too many Flash videos. While both the 11-inch and 13-inch models have slower processors than MacBook Pros, the machines feel surprisingly zippy, and are more than powerful enough for most everyday uses. On Monday, Apple updated the processors in its Air lineup once again, and it also reduced the price of its 13-inch model by $100. That machine now sells for $1,199, while the 11-inch Air still goes for $999.

At these prices, the Air is unbeatable. There are lots of computers that are cheaper than the Air—including several thin and light “ultrabook” laptops that PC manufacturers have released to mimic the Air—but they lack the quality and responsiveness of Apple’s machine. The cheap Windows ultrabooks I’ve tried have been blighted with poor trackpads, bad battery life, and glitches (for instance, a failure to respond quickly after being placed in standby mode). There are some well-reviewed ultrabooks on the market (like the Asus Zenbook), but these generally go for around the same price as Apple’s Air, and they’re still not as good as the Air.

Meanwhile, machines that are more expensive than the Air don’t make much sense. This is especially true of Apple’s non-Retina MacBook Pros, which start at $1,199 for the 13-inch model and $1,799 for the 15-inch. These machines seem to offer better specs than the Air—they have faster processors, optical drives, and more storage space—but I suspect that for most people, those specs aren’t worth the extra weight. Many people worry about the Air’s limited storage space compared with hard-drive based laptops, but I don’t think you’ll have many problems. If you separate your data from your computer using external storage—put all your photos, music, and video on a backup drive and on services like Dropbox—you really don’t need many hundreds of gigabytes of onboard storage these days.

If you study the success of the Air, and the efforts of PC makers to clone it, it seems obvious that over the next few years, every new laptop will have its thin and light frame. Apple has made clear that the new Retina MacBook Pro is the future of the MacBook Pro line; look for that model to get cheaper over time, and soon—if not next year, then certainly in 2014—it will replace the hard-drive-based MacBook Pro.*

The mystery is what will happen to Apple’s laptop line as it picks up more and more features that we associate with the iPad. Like Apple’s tablet, the new MacBook has a Retina display, and it boasts seven hours of battery life, which is closing in on the iPad’s 10-hour mark. At some point Apple’s laptops will add touchscreens, too—touch will be too widely embedded in the computing culture for laptops not to have it. At the same time, the iPad will get faster and faster, in time matching the power of today’s laptops. And all the while, the Mac OS will keep picking up more and more features that Apple first showed off on its mobile OS.

What happens when these trends collide? In three years’ time, what will be the difference between a $499 iPad and a $999 MacBook? Will they be essentially the same machine, except that one will come with a keyboard and one won’t? The same question applies to Windows PCs, too, as Microsoft’s upcoming Windows 8 is meant to enable the convergence of tablet and desktop operating systems. Will there soon be no difference between Windows tablets and Windows laptops, either?

I don’t know the answers to these questions. But the dynamics sure are strange and fascinating to behold. Thanks to Apple, laptop computers have never been better. And, also thanks to Apple, laptops have never been more clearly destined for obsolescence. Let’s just enjoy it while it lasts. After all, a faster, less smelly horse would have been pretty awesome, no?

Correction, June 13, 2012: This article originally stated that the new model of the MacBook Pro will replace the hard-drive-based version “if not next year, then certainly in 2013.” It should have read “if not next year, then certainly in 2014.” (Return to the corrected sentence.)