Based on several thoughtful exchanges in previous threads, I instantly thought of Spiritual Lefty while reading this piece by Don Boudreaux in which he comments on some points made by Jeffery Sachs in his latest book, Common Wealth , in which Sachs discusses some of his signature issues like world poverty and sustainability.

Boudreaux cites this quote from page 23 of Sachs's book:

I will argue at some length that this is too many people to absorb safely, especially since most of the population increase is going to occur in today’s poorest countries. We should be aiming….to stabilize the world’s population at 8 billion by mid-century.

As I read that quote, I could already see where Boudreaux was going with his argument and I can't say I blame him. Here's the gist of it:

First, he has obvious problems with the arbitrary number "8 billion". He considers it worthless...as do I.

Boudreaux:

He could have dreamed it up in his sleep, or taken it from a multi-year study conducted by a lavishly funded committee made up of the world's most accomplished economists, demographers, environmentalists, statisticians, physicians, and other Very Smart Experts....There is simply no way to know how many persons the earth can "support" in the year 2050 (or any other year, for that matter).

Agreed. In a way, it's well-meaning arrogance...but arrogance nonetheless...to claim to know such things. Sachs is using obsolete information to make such an assertion....and by "obsolete", I mean "from the present" in the context of some 40 years from now. I'd be curious to see what Sachs would said 40 years ago. I'll bet he'd have been dead wrong about almost everything of import.

But here's the crux of Boudreaux's critic, in which he puts to succinct words, an excellent example of my variation of Hayek's Fatal Conceit:

A much deeper problem with Sachs's eight-billion number is that, in calculating it, there is no way to predict how human creativity will alter the world during the next 42 years. It's ludicrous to pretend that we can know now what, say, the average MPG will be for internal-combustion engines in 2050. Hell, we don't even know if automobiles and lawnmowers and the like will still use such engines then.

Bingo. Excellent. The hubris of pretending to know future circumstances based on limited current knowledge and making assertions therefrom.

Boudreaux challenges that hubris of pretending to know by asking us to think from 1966 knowledge about our modern world and inconceivable innovations enterprising people have made and built upon. Aside from all the high tech stuff (which does indeed affect our resources), he cites a favorite example of mine: Aluminum cans...which use perhaps an 1/8 (?) of he metal used as late as the 70s. Any predictions back then about future Aluminum use are useless for this simple reason.

Here's the bottom line that Sachs needs to appreciate:

There is no way -- literally, no way -- to know how technology and social institutions will change between now and 2050. Given this impossibility -- and given the fact that we can nevertheless predict with confidence that technology will advance and that social institutions will change -- to assert that "optimal" population in the year 2050 will be eight-billion persons is ludicrous in the extreme. It's faux-science, and deserves only ridicule.

I concur...to say the least. Human History's biggest positive lesson for the future at any given time (I say "positive" because there's plenty of negative lessons about war, oppression and misery by the state) is that human creativity, innovation and adaptation are constants whose effects on future circumstances, though unknowable in terms of detail, are certain and always around the next corner.