When Microsoft unveils the consumer editions of Windows 10 next week, key questions about the OS will be on the table. Will Windows remain relevant? In a world of choices, would you willingly choose Windows 10? And in a business where others make these choices for you, would they choose Windows 10?

Its been said that, for people to want Windows 10 more than they did Windows 8, the system needs to return to many of the designs, themes, and functions of Windows 7. Well, theres already one competitor purporting to have all of Windows 7s most beloved features, and that competitor is called Windows 7. True, theres something to be said for the persistent value of familiarity just look at BlackBerry’s turnaround strategy, anchored on producing devices that remind people of BlackBerrys.

But reruns are cheap. If Windows 10 is merely a retread, people will make do with Windows 7 a year or two longer, and Windows 10 wont succeed. The opportunity would arise for a competitor to seize the moment. At the other end of the scale, if Windows 10 adopts yet another new user experience that reminds the veteran user of nothing whatsoever, it wont succeed. Wednesdays event at Microsoft’s Redmond, Washington, headquarters will be a high-wire act for Microsoft, but this time theres no safety net.

This will be a consumer-focused event, although businesses will also be watching the proceedings, which will be webcast and feature top executives including CEO Satya Nadella.

For all the reasons Windows 8 was rejected by businesses, the main reason was enough: Retraining employees comes at a sizable cost. So it will be incumbent upon Microsoft to produce, borrowing a legal phrase, a plea for continuance: a reason for users to keep believing in the potential of the product until at least next fall.

To pull this off, Microsoft has to prove to its customers the following:

1. The Windows 10 usage model can be both familiar and new. Usage model means the methodology, but also the philosophy, behind using the product. Facebook has a usage model thats fundamental to its entire platform on all devices. Microsoft must have a similar usage model in mind for Windows 10.

Windows Mobile tried to appear familiar to phone users by looking like a PC, with a start menu and a taskbar. That failed. When Windows 8 tried to appeal to PC users by looking similar to the compact, tile-strewn world of Windows Phone 8, that failed too. Users dont want one device to look or act like the other, and they dont need both devices to be used the same way, in order for them to perceive both systems as Windows.

However, people do need one familiar place that brings together their documents, services, and applications no matter how many devices they use. If Microsoft can borrow a page from Dropbox and Evernote, it could represent Windows as a place they can reach from their devices, rather than a file system that needs to be synced with other file systems. This way, devices dont have to work the same way for them to accomplish the same goal.

2. Windows 10 is a service that bridges individual devices. If the huge number of Windows users are to become Windows subscribers, they need to begin perceiving Windows as a service. Newspapers dont charge individual fees for each device from which you read their online publications, and neither should Microsoft.

Microsoft does not need to reveal Windows 10s retail price just yet. But if it divulges no information at all Wednesday about how its subscription model will work, then Windows Phone 10 will gain no more users than it already has. If Windows truly is the same system for both classes of device, then why shouldnt a subscriber be entitled to it everywhere?

3. The ideal of Windows is a cause that everyday people can support. Such a cause must be practical, achievable, and desirable.

Apples iOS and Mac users believe in Apple as a cause. They perceive the company as upholding principles of usability, excellence in design, simplicity, and practicality. It just works is a phrase the Apple loyal are proud to say aloud. To some extent, Google has managed to cobble together a workable ideal for Android, around the principle that it belongs to you. As a company, it successfully portrays itself as a responsible, diverse, and moderately liberal corporate citizen, advancing itself as a model company for other companies.

The last ideal that Microsoft attempted to articulate for its base was, I am a PC. Thats exactly the wrong cause for the mobile era. While CEO Nadella has cast Microsoft in the new role of a “platform and productivity company,” the ideal people will rally behind is not a vision for Microsoft but rather a vision for society. It won’t be a product goal, like great user experiences, but a vision of work being done and life being lived.

Microsoft has started down this path before, and has occasionally made headway. Now the company needs to tie that vision directly to Windows, so that if someone pasted a Windows logo to his back windshield, his neighbors wouldnt think he was weird.

Well be tracking Microsofts progress towards proving these three points, beginning Wednesday before 9:00 am Pacific Time. Follow our coverage of the Windows 10 preview event, including our Twitter stream at @SMFulton3.