First is the belief that a few well-meaning individuals can make a difference.
Turning a few lights off is not going to stop global warming. Turning a power station off could. Reducing your own consumption of oil by a few litres is not going to make a big difference. Reducing a country's imports or reducing a company's output by a few million barrels is. Throwing a few tins into the recycling is not going to save the world. It's just a tiny drop, and the drop is probably of molten melted in an oil-fired crucible.
The second, much more dangerous assumption is that a few well-meaning individuals won't make a difference. Most of the critical decisions that could affect our survival are going to be taken by individuals. The important actions are going to be made by individuals. Leaders of businesses, heads of governments and representatives of organisations are all individuals. Every policy and paper starts from the pen of one person. The only people who can make a difference are well-meaning individuals. You may be one of them. Somebody you know may be one of them. Somebody who happens to see one of your trivial deeds may be one of them.
Human actions are influenced in many ways, and it's not always clear why things happen. This is why people can get advanced degrees and influential jobs in economics and still sound like complete idiots.
But just when I was worrying about my own actions making no difference at all. Just as I was settling into the realisation that the main results of my noble attempts to change the world through building a house had all long since gone in and out of the bank accounts of various agents in the industry, who are now back to their inevitable unecological tricks. Just when I thought it was all a waste of time, the water bill came. Nothing unusual about that, but on it was a piece of advice. It said something like this: to avoid your pipes freezing, be sure to put some insulation, for example expanded polystyrene, around the main tap.
Now I know this is a small thing, and it would be a lot more useful if the invoice for heating bills suggested you insulate your whole house, but that may be like expecting the people in the hamburger shop recommending you drink water rather than a large container of brown fizzy sugar, or saying "are you sure you want fries with that?"
But it's a positive thing. It's much better than the usual solution, which is wrapping pipes with an electrical heating element that comes on whenever the temperature gets anywhere near zero. I'm sure it does not directly result from my building project, but somebody out there is making some sensible suggestions, and I'm not a lone crazy voice shouting into a wilderness.
