Changing the built environment to allow step-free access - an exercise which is costing a huge amount of money, and if you consider London's tube network, has really only just begun - is a good thing. I have pushed buggies and I still push a wheelchair from time to time, and the world has got better over the last few decades for the millions of us who do this.
But the move to Flatworld is not without a downside, and this doesn't seem to be discussed much.
Making the world safe for wheelchairs and buggies has also made the pavements safe for tourists with luggage on wheels that is too heavy to lift; for badly controlled infants on scooters and badly behaved adults on roller blades (and bicycles); and, in a further contribution to the continuing atrophying of human muscle power, for the Segway.
Anything that had George W Bush as a famous early adopter needs to be looked at with suspicion.
Here at Port Soller in Mallorca, for example, a huge sum of public money has been spent in recent years on public realm improvements along the waterfront. It is all to a high standard, and as we expect of such projects now, everything is step-free.
And so a shop on the waterfront offers Segway tours - which would not have been possible before the improvements. You get to see the waterfront, like on foot but faster, and to the irritation of pedestrians.
There are two main downsides to step free access.
First, letting onto the road anyone who has a good reason to be on wheels on the pavement - such as a wheelchair user - for example to cross a side street via dropped kerbs - has the undesirable consequence of letting anyone who should be on the road - such as a cyclist - more readily onto the pavement. And it makes the use of things such as roller blades on pavements, not always found on the feet of considerate people, easier for those who want to do so. The general elision of the world of the road and the world of the pavement - in principle a good thing, in the introduction of the shared surface - encourages the take-up of new things that don't obviously belong to one or the other, like the versions of infants' scooters that are used by grown ups - some versions of which are powered.
The second, related downside is less activity for the able bodied, particularly if they are predisposed to avoid physical effort, as most of us are. Someone in a wheelchair needs a lift to get the first floor - the able bodied don't, but they tend to use the lift anyway - and most new buildings are arranged to hide the stairs away. Encouraging walking by improvements to the built environment is a public policy objective intended to improve health, but there are all sort of things that make it easier not to get incidental exercise, such as by climbing stairs or carrying bags, than it used to be.
While shoes with integral wheels don't seem to have caught on yet for the adult market, this may just be the result of an image problem, as so far they have mainly been aimed at children. But that doesn't seem to put off grown-up roller bladers and skateboarders. As it becomes more and more practical to get from home to work with wheels on your feet, the practical means will surely soon be provided for everyone to do this.
The Incas knew about the wheel, but used it only for small objects with no practical use, like toys. No flat surfaces to use wheels on, you see. The Incas didn't last. The future appears to be flat.