BUILDINGS aren't just to live in or look at.

They define the societies that create them.

When we go to Durham Cathedral, we marvel at how faith and ingenuity helped people overcome primitive technologies to create a miracle in stone. When we pay our entrance fee into Castle Howard or its like, we think of the style and opulence of their creators' lifestyle; they exploited others to get their money, but didn't they know how to spend it.

Finally, when we walk into a town hall, like the one I am in today in Middlesbrough, we think of how the concepts of civic pride, duty and public service took root in the 19th Century and created towns and cities out of chaos and squalor.

When some future historian picks up the pieces of our society and looks for a clue to what we were all about, I don't think they'll choose a sacred or a civic building. My guess is that they'll go for a supermarket.

Supermarkets are the churches of the 21st Century, places where people go to worship at the altar of consumerism, the biggest and weirdest cult of all.

That's why this week's report on the supermarket "big four", who control 75 per cent of a £123bn market, is important to those who shop until they drop and to those of us who check in at the check-out as rarely as possible.

With their land banks, purchasing power and influence, supermarket bosses are a bit like the feudal overlords of times gone by. Are they benign bosses - or robber barons?

The Competition Commission report drew no firm conclusions. It criticised the way supermarkets treat suppliers. Paying a farmer 16p for a litre of milk that costs 19p to produce doesn't leave him much to live on, let alone work in more environmentally- friendly ways.

BUT, it concluded, consumers love the laden shelves of their supermarkets. So it is no bad thing if they multiply and grow bigger.

But we have to ask where this growth will lead. One in ten car journeys in the UK is to a supermarket.

That supermarket may contain 60 times more goods than a little corner shop, but it emits 60 times as much greenhouse gas. Then there are air miles and impact on agriculture in other countries, many with a fragile environment, caused by our apparently insatiable appetite for something new, something different.

This week, I popped into a small café run by some friends in Middlesbrough. They probably didn't realise, but their buying policy was a model of greenness and self-sufficiency. Milk, fruit and vegetables, bread, you name it, it all came from traders in the same mall. The suppliers were like themselves, small local businesses co-operating and combining to survive and hopefully prosper.

I'm sure that if one of the flash management consultants who run - or should that be ruin - so many of our big businesses heard about this, they would tell them they were doing things wrong.

Their advice would be cut costs, buy big, treat your neighbours as competitors not co-workers.

That advice might save them a few pennies, but their business would lose its identity, its human touch. That is something, I believe, that people value more than a knock-down price on something, they probably don't need anyway.

The little place I visited knew that self-sufficiency can also mean cost-efficiency and also appreciated it was part of a trading community - and a wider community - and that it had responsibilities to both. I wonder how many of our global giant retailers can say the same.

We have got to take a hard look at how we spend money and the ethical and environmental principles of the companies we spend with.

Otherwise, when those historians I mentioned come to look at our monuments, they will marvel not at what we built, but at what we destroyed.