Of all the differences between a Mac and a PC, few are as obvious as the mouse.

Mice for Apple Computer Inc.'s Mac have but one button, while mice for Microsoft Corp.'s PC have at least two and usually a scroll wheel nestled between them.

As a Mac user since 1993, and an Apple IIGS user before that, I have subscribed to the one-button mouse philosophy for a long time. Like many Mac users, I've always thought of the one-button mouse as one of the Mac's distinguishing features.

But I recently bought a two-button optical mouse with a scroll wheel to avoid my iBook's track pad.

I had a revelation.

Plugging the new mouse into my desktop tower Mac to test it, Mac's OS X software recognized it instantly. After using the new mouse for a few hours, I knew the Apple Pro mouse that came with the tower Mac was destined for the iBook's carrying case.

I realize that some in the Mac community may consider this blasphemy. The one-button mouse, perhaps out of sheer longevity, has become an article of faith with many Mac users. Whenever the issue of Apple adding a second button or a scroll wheel to its mouse comes up, words fly.

"I hate two-button mice SO much," wrote someone to a MacRumors.com forum in March in response to a posted rumor that Apple had created such a mouse and had planned to introduce it this fall.

"Why would Apple go and change their whole one-button concept?" wrote another Mac user. "If you want one more button, go out and get another USB mouse with more buttons -- it's not that expensive."

But those already using a two-button mouse were defiant. "I wouldn't give up my other button and the scroll wheel ever," one convert wrote. "Not ever. And I think I'm way more efficient with these features."

"Efficient" is the operative here. With a one-button mouse, Mac users need only to press the control key while clicking to get a contextual menu -- a pop-up list of options that varies according to where the mouse pointer happens to be.

And navigating through long documents requires moving the mouse pointer along the scrollbar on the right side of the Mac's window.

The right button makes contextual menus available with one click. Now that I have a second button, I make far more use of contextual menus. And I've become so accustomed to using the scroll wheel to browse Web pages that my finger keeps looking for it on the single-button Apple mouse on my Mac at work.

Multi-button mice provide the same conveniences in Mac OS 9, though support is not built in. Enabling the extra features in OS 9 requires the extra step of installing a control panel -- a simple drag-and-drop operation.

But with my eyes now opened to the advantages of a more capable mouse, I'm annoyed at Apple's stubborn commitment to the single-button variety. Dozens of third-party mice are available, but why would Apple include support for these devices in OS X but fail to supply such a device itself?

When asked, Apple touts the support OS X provides for such Universal Serial Bus-input devices as joysticks, trackballs and multi-button mice -- but the company won't comment on whether a two-button mouse is in the works, or ever will be.

This stance isn't surprising, as Apple never comments on unannounced products. Still, it doesn't answer the overriding question: Why no two-button mouse?

It most likely may have something to do with history.

The the one-button mouse dates back to 1980, the beginnings of Apple's Macintosh project, four years before the machine was introduced to the public.

Jef Raskin, the project head in those early days and the long considered to be the "father" of the Macintosh, has said the one-button mouse concept originated with him.

In "Making the Macintosh: Technology and Culture in Silicon Valley," Stanford University's Web-based history of the Mac's development, Raskin explained what happened.

The laboratories at Xerox Corp.'s Palo Alto Research Center, the California-based facility where Apple engineers drew the inspiration for the point-and-click interface that was to evolve into the Mac, used a clunky three-button gadget.

"I had observed," Raskin said, "in myself and others, that the three-button mouse was confusing. And I said, 'What would be the way of making it so there would never be any question about what button to press?' If there's only one button, you can't make any mistakes."

Since one of the design goals of the Mac was to make a computer that was easy to use, the one-button mouse was a self-evident choice.

That was 20 years ago, however, when computer users had to type every command. Today, most of the population has computer experience -- and experience with a mouse. And in our Microsoft Windows-dominated world, 95 percent of those computers are PCs with a two-button mouse.

Indeed, Apple's one-button mouse is a potential sticking point for the Windows "Switchers" the company is courting aggressively in its current advertising campaign.

So while Apple's decision to go with a single button was one of the many choices that made the original Mac such a groundbreaking machine, it's time for Apple to reconsider.

Longtime Mac devotees may disagree, but an official Apple two-button, scroll wheel-equipped mouse has, in fact, no apparent drawbacks.

The simplicity argument has eroded over time. Few novice users would be confounded by a second button; the use of the scroll wheel is obvious. Those who prefer not to use the extra button or scroll wheel don't have to. They can stick with the left button until they're ready to experiment with more advanced mousing methods.

Many veteran Mac users would discover advantages they never knew existed.

Now, I'm not advocating a three- or four-button-mouse. I've even seen mice with six buttons! That's too many for a standard-issue device, and surely would confuse many users. But since Mac OS X already supports a second button and scroll wheel, it only makes sense to give people the corresponding hardware.

For those Mac users still clinging to their single-button mice, don't knock it until you've tried it. You may discover a side of your computing self you never knew existed.