Dear Mr Krugman,

I was attracted to your op-ed in today's (Friday's NYT, "The Free Lunch Bunch") by what you said about a "basic principle of economics" stating that there is no such thing as a "free lunch ". It reminded me of something that my parents often said to me as a child: that "money doesn't grow on trees ", which is just another way of expressing the same thing, of course.

When the economy is looked at as a whole (and over time), it is a valid statement, just as in physics the conservation of mass and energy is (notwithstanding the ultimate "free lunch" provided by the big bang).

However, looked at from a more local perspective, there certainly are "free lunches" to be had (or if not entirely free, certainly well below cost price). It is just that someone, somewhere or sometime has to pay (the full price) for them.

When someone inherits a million dollars and invests it at a modest annual return of say 5 percent, they are making $ 50,000 a year without lifting a finger. If that is not a "free lunch", or like having a "money tree" in your back garden, I don't know what is.

And by consuming Earth's natural resources (particularly fossil fuels) as if there were no tomorrow, are we not gorging ourselves at very low personal cost, but ultimately at a very high cost to our children and coming generations?

Man is an animal (the planet's Greatest Ape), behaviourally programmed and conditioned by millions of years of evolution to struggle for survival and advantage in his natural environment (and always on the look out for a free or cheap lunch). With the advent of civilisation, the focus of this behaviour has been transferred to the "socio-economic environment ", and free-market capitalism has been honed to take full advantage of it.

We (as individuals, groups, companies, even nations) are so preoccupied with the struggle for survival and advantage in the socio-economic environment (the local, national or global economy), which largely boils down to making money, that we have all but lost sight of our ultimate dependency on the natural environment.

But as you say, "It is difficult to get a man to understand something when his salary depends on his not understanding it."