John McCarthy's main page concerns computer science, especially artificial intelligence. I am a professor of computer science (now emeritus) at Stanford University and this web site is a spare time activity that I hope will do some good. Here's more about me.


This Web page and its satellites are aimed at showing that human material progress is desirable and sustainable. People have worried about many problems. These pages discuss energy in general, nuclear energy, solar energy, food supply, population, fresh water supply, forests and wood supply, global engineering, pollution, biodiversity, various menaces to human survival, the role of ideology in discussing these matters, useful references. Other problems are discussed in the main text including minerals and pollution.

The sustainability pages are essentially done, although I plan to improve them and respond to inadequacies people find. Having done my best to show that material progress is sustainable, I can justifiably turn my attention to the future and present ideas about what progress people will want and what can be achieved. The emphasis is on opportunities rather than on inevitabilities.

Most of the contentions of these pages are supported by simple calculations based on readily available numbers. Here's an illustration. Slogan: He who refuses to do arithmetic is doomed to talk nonsense.

With the development of nuclear energy, it became possible to show that there are no apparent obstacles even to billion year sustainability.(1) . A billion years is unimaginably far in the future.

Humanity has progressed over hundreds of thousands of years, but until about the seventeenth century, progress was a rare event. There were novelties, but a person would not expect a whole sequence of improvements in his lifetime. Since then scientific progress has been continual, and in the advanced parts of the world, there has also been continued technological progress. Therefore, people no longer expect the world to remain the same as it is. [Very likely, the greatest rate of progress for the average person occurred around the end of the 19th century when safe water supplies, telephones, automobiles, electric lighting, and home refrigeration came in short order.]

This page and its satellites will contain references to articles, my own and by others, explaining how humanity is likely to advance in the near future. In particular, we argue that the whole world can reach and maintain American standards of living with a population of even 15 billion. We also argue that maintaining material progress is the highest priority and the best way to ensure that population eventually stabilizes at a sustainable level with a standard of living above the present American level and continues to improve thereafter.

These opinions are old-fashioned according to some people, but they have a lot of support. For example, the biologist E. O. Wilson writes in his excellent book Consilience.

In contrast to widespread opinion, I believe that the Enlightenment thinkers of the seventeenth and eighteenth centuries got it mostly right. The assumptions they made about a lawful material world, the intrinsic unity of knowledge, and the potential for indefinite human progress are the ones we still take most readily to heart, suffer without, and find maximally rewarding as we learn more and more about the circumstances of our lives.

[I'm not claiming Wilson would agree with everything on these pages or even most of it. Indeed I think his last chapter has too much overly standard environmentalist pessimism. Wilson's 2002 book, according to a review I saw, makes it clear that he would not. I see it as a retreat into sentimentality from what he wrote above.]

I offer no opinion about a "right" population, and I suspect that population will eventually be limited by a sense of crowdedness rather than by material considerations. Here's a more extensive discussion of population. There is a widespread belief that the present standard of living of the advanced countries is not sustainable and not extendable to the present backward countries. I and many others don't agree. This exposition mainly concerns scientific and technological bases for optimism rather than the historical and economic arguments ably advanced by Julian Simon, who died suddenly in 1998. Simon's web page contains much of his work.

There are some menaces, but they are likely to be avoided. In contrast to the menaces there are technological opportunities. I'm pleased to see that the opportunities are slightly ahead of the menaces in numbers of hits.

I consider these pages essentially finished as far as showing that material progress is sustainable. I have gotten into some arguments about what present policies are good and bad, and pages concentrating on that would require continued updating. However, I think I have enough to show sustainability.

Frequently asked questions about sustainability of progress

Q. What is meant by material progress?

A. Human progress in the last few centuries has included the following.

All this progress was a consequence of the advance of technology and also of advances in government and other social organizations in capitalist society. These other social organizations include universities, societies for the promotion of the arts and sciences, trade unions, publications, political parties, and advocacy organizations. Mainly it was technology, which became increasingly based on scientific discoveries.

None of these advances ensure that everyone will be happy. The American Declaration of Independence wisely offers only the pursuit of happiness. However, I believe that progress has resulted in less acute unhappiness. Someone who thinks otherwise should explain how parents were just as happy when half of their children died in childhood.

All these things are dependent on the material wealth of society. People can dispute about how to divide the wealth, but there has to be wealth to divide. Here are some of the questions that have led some people to believe this progress can't continue and some answers to their worries.

Q. Can the world grow enough food for 15 billion people?

A. Yes, it can and with present agricultural technology. With better technology, probably a lot more. Biotechnology based on molecular genetics is just beginning to be applied to agriculture. How much land can ten billion people spare for nature? by Paul E. Waggoner of the Connecticut Agricultural Experiment Station discusses how agricultural productivity has grown worldwide and why the growth should be expected to continue.

Q. Aren't our forests being exhausted?

A. No. In the industrial countries, the land in forest is stable and the quantity of wood is increasing. In the tropical underdeveloped countries, there is still substantial conversion of forest to agriculture. Here are some facts about forests.

Q. Is humanity suffering from an enormous loss of biodiversity.

A. The loss is quite small of the important or individually interesting species. Here is a beginning on biological diversity. There's not much there yet, but there is an adequate discussion in the references given there.

Q. Isn't the world running out of energy.

A. No. Nuclear and solar energy are each adequate for the next several billion years. That's right; billion not just million or thousand. See the discussion of Energy Problems for the general discussion and the summary of Bernard Cohen's article justifying a 5 billion year estimate.

Cohen's 5 billion year estimate is based on extracting uranium from seawater, which the Japanese have already shown to work. Most likely, it will be cheaper to use lower and lower grade ores on land, but no one will spend the money to develop the technology to use low grade ores until high grade ores begin to run low.

Q. Isn't it important to conserve energy?

A. Energy needs to be regarded as just another commodity, to be used in whatever quantity is cost-effective. It is available in whatever amounts may be needed. Treating its conservation as a special goal has been wasteful of human effort. We are the poorer for it.

Indeed before the oil crisis of 1973 energy was just a commodity. Different kinds of energy had their costs in different markets and users of energy minimized energy costs along with all their other costs. The oil crisis combined with the growing anti-establishment sentiment that equated nuclear power with nuclear weapons was just one of the reasons why energy came to be regarded as a thing apart.


Q. When will we run out of oil?

A. Twenty years ago, I had been convinced that by the end of the 20th century we would be out of oil directly pumpable from the ground. Obviously, we aren't, and I am cautious about how much oil there is left. Maybe 20 years, maybe 50 years, maybe 100 years, but I can't see it lasting longer than 100 years.

However, oil can be extracted from oil shale, from tar sands (as it is in Alberta, Canada) and synthesized from coal. These processes (except for tar sands) are too expensive to compete with just letting it just flow out of the ground in Saudi Arabia, but the technologies were developed when it was thought oil would run out soon. The costs would be affordable. Taking these sources into account we probably have several hundred years supply of oil, provided "greenhouse" warming and soot pollution permit its continued use.[2002 March 20: New studies claim that submicron particles from power plants are more harmful to health than previously thought.]

Q. What will happen when all these sources run out or if global warming requires severe restrictions?

A. Oil is readily replaced by nuclear energy for electricity generation. However, it is not so readily replaced for transportation. If we can develop good enough batteries, electric cars are a solution. If not, liquid hydrogen will work for cars and trucks. Other solutions are being promoted these days, e.g. compressed gaseous hydrogen, but I don't see anything but liquid hydrogen that will both avoid the emission of CO2 and give the range of gasoline powered cars. In the end, I don't think we will give up the range. 2003 note: It doesn't look like batteries will make it for cars in spite of enormous expenditures.

Q. What about airplanes?

A. Hydrogen seems rather bulky for airplanes, although some experts think that the advantage of having less weight for given energy will outweigh the disadvantage of having more bulk per unit energy.(8) Most likely, we can continue to use oil, probably synthetic, for the indefinite future. If airplanes become the only major source of putting CO2 in the atmosphere, then the atmosphere can get rid of that much CO2 without significant warming.

Q. What about the non-fuel uses of oil and natural gas? Don't our plastics depend on their availability?

A. Oil and gas are used as feedstocks for making plastics of all kinds, but the amounts are much smaller than their use for fuel. Any source of carbon will do in place of oil and gas - coal or biomass, for example. Oil and gas are used today, because they are cheap, easy to handle and carry the energy required for the chemical reactions along with the materials. (7)

Q. Will we run out of minerals?

A. No. There is plenty of every element in major use. It is a question of the economic concepts of reserves and resources. Iron ore and aluminum ore are presently obtained from very rich ores available in a few places in the world. These ores can be shipped long distances by water at small cost. They are oxides rather than the silicates which present refining procedures don't handle. The earth's crust is 5 percent iron and 7 percent aluminum, but most of it as silicates. Refining silicates will require more energy. However, the extractive industries only account for four percent of the American GDP, so we can afford more expensive extraction processes when they become necessary.

Indeed once we can extract minerals from random rock, the only way of running out of an element is to eject it from the planet or to let it subduct under a continent. This is because using quantities of elements doesn't destroy them. Therefore, the scrap piles will eventually be ores. This won't happen for a long time, because more concentrated ores will remain available for a long time.

In fact metal ores have become more inexpensive recently as is illustrated by the famous bet between the environmentalist Paul Ehrlich and the economist Julian Simon. In 1980 Simon sold Ehrlich (on credit) ten year futures on five metals of Ehrlich's choosing. The total price was $1,000. In 1990 Ehrlich had to pay Simon $600, because the metals had gone down in price.

Copper is presently being mined in the U.S. at a concentration only ten times its concentration in the earth's crust.

Q. Doesn't the second law of thermodynamics tell us that the lower the concentration of the ore, the more energy it takes to extract it?

A. It does indeed, but the energy required goes up very slowly as the concentration goes down. To separate one mole of a substance from n moles of a substrate requires an energy RT ln n according to the second law. According to this formula, it would pay to extract one atom of uranium from the entire earth. Of course, mineral extraction is more expensive than that, but the second law of thermodynamics isn't the reason. Detailed calculations of the energy costs dictated by the Second Law of Thermodynamics and a comparison with current prices is given.

Q. What if the population increases?

A. There is certainly a limit to the population the earth can support, and migration into space can only occur very slowly at the present level of technology. The limiting factor may be food, but a feeling that enough is enough may be more important. We will see what happens when 10,000 people try to post to a usenet newsgroup. That won't require any increase in population - only an increase in the availability of computers. Nevertheless, it will give everyone a taste of a more crowded world. Some people ascribe the increased crowdedness of American national parks to the increase in population. However the number of visitors to Yosemite National increased 2.6 times as fast as the population of the U.S. or of California. The crowdedness is caused by increased equality of opportunity to visit the parks.

Q. How fast is population increasing?

A. In the U.S., Europe, and Japan, the birth rate is below the level required to sustain the population. The population is increasing because of immigration and from the baby boom that followed WWII. It is the grandchildren of the boomers that are keeping the schools going. See the page on population.

In much of the rest of the world the population is still increasing, but the rate of increase is slowing, especially in the big countries of China, India and Indonesia.

There is still a high rate of growth in Africa south of the Sahara, but it also shows signs of slowing.

Q. Is the population problem urgent?

A. Only in a few countries, and it is their problem, because they have sovereignty. People in the advanced countries can only provide technology, but adequate birth control technology has already been provided. For the world as a whole, the population problem may be important, but it is not urgent.

Even for Bangladesh, bad government seems to be more the problem than population per se.

Q. Isn't the world running out of usable fresh water supplies.

A. No, but some countries may have to spend a lot of money on water projects, just as our ancestors did. For more, see the water FAQ

Q. What about the ozone layer, the ozone hole and UV-B?

A. On the theory that chlorofluorocarbons put chlorine in the upper atmosphere which destroys ozone, their manufacture has been banned. A 90 percent reduction would have been just as effective and less economically disruptive, but industry seems to be adjusting to the total ban. Here's more about ozone

Q. Won't global warming do us in unless we drastically reduce our use of energy?

A. No. Global warming can be avoided or reversed should it turn out to be a serious problem. However, there is a thorough paper Why Global Warming Would be Good for You by Tom Moore of the Hoover Institution. See (5) for a reference to some critiques - mostly ill-tempered. It is still controversial whether global warming from CO2 is occurring or whether recent warm years are a statistical fluctuation or a consequence of changes in the sun.

Here is Health and Amenity Effects of Global Warming, also by Tom Moore. It offers statistical evidence that regions of the U.S. with warmer climates have lower death rates and also are preferred to colder regions. Also death rates from most causes are greater in winter than in summer.

Two scientific skeptics about the harmful effects of global warming are Richard Lindzen of M.I.T. and Frederick Singer of an organization called SEPP. I don't give links but suggest googling them, because they have written both on their own pages and for various publications.

Warmer winters seem to have increased wheat yields in Australia.

Q. What about trash and garbage? Aren't we likely to drown in them?

A. The U.S. produces about 375 million tons of trash and garbage per year. There is no real shortage of land where it can be put. It should be piled quite high. What changed is that before the recent enthusiasm for wetlands, filling in swamps with garbage was the approved thing to do, and the land was available without cost. Now it must be paid for, but the costs are quite bearable. Suppose trash has a density of 1.0, i.e. equal to that of water. Suppose it is piled 10 meters high. Then we are using 37.5 square kilometers of land for landfill per year.

Q. Given all this uncertainty about the prospects for continuing material progress, isn't it better to be safe than sorry?

A. Yes, but material progress is much more likely to be safe than is stagnation. The proposals for limiting progress are likely to cost lives from poverty and make humanity less capable of dealing with the inevitable emergencies. The proposals claiming that safety lies in restraining progress are more likely to lead to sorrow than continuing progress in general.

Q. Isn't the static American standard of living evidence that some things are getting short and hence more expensive. [1999 December note: The perception that the American standard of living was static turns out to have been a journalistic blip.]

A. No. Food, minerals and many manufactured goods continue to decline in price. What has gone up are medical expenses, bureaucratic expenses of all kinds, social security payments and costs of meeting environmental and safety regulations. People voted for these expenses, and the perception that the standard of living hasn't improved may be based on discounting all these increased expenses as not actually contributing to the standard of living. With all that it is not certain that the standard of living has been static. Maybe it is just that those who "turned on, tuned in and dropped out" are facing some of the consequences. Moreover, our whole society is facing the consequences of so many people having found education to be irrelevant.

Q. Have environmental and health and safety regulations been expensive to our society.

A. Yes, they have cost about $625 billion per year according to one estimate. [Other estimates are different.] My opinion is that many of the regulations have been worthwhile, but a great many (probably most) have contributed very little when compared to the costs they have imposed on individuals and businesses.

However, our society can survive even a large amount of irrational regulation. I remain an extreme optimist.

Q. Aren't the people of the advanced countries using more than their proper share of natural resources?

A. People can really be said to use more than their share of something if their use deprives someone else of it. If there is plenty for everyone for the indefinite future, the concept of fair share is meaningless.

The only major commodity whose use in the advanced countries may deprive people of the poor countries in the near future is petroleum. How near is the exhaustion of petroleum is not clear.

When the petroleum supply shows clear signs of running out, perhaps the advanced countries should give the poor countries some extra help in making the transition to nuclear and possibly solar energy. By the time petroleum runs out some, maybe even most, of the presently poor countries will no longer be too poor to solve their own energy problems. Any country, which like the U.S. today, spends only 8 percent of its GDP on energy can afford to solve its own energy problems.

Q. What does it matter whether we believe progress is sustainable or not?

A. Important policies depend on it.

  1. If progress were not sustainable, then it would be important to reduce consumption of whatever resources were limiting progress. It would be the particular duty of the countries using the most of these resources.
  2. Since progress is sustainable, and there is no limiting resource in the short term (next few hundred years and probably much longer), the most important way to help the poor countries is to help them develop more or less along the path pioneered by the richer countries - skipping some steps when possible.
  3. The richer countries should continue their progress, both for the sake of their own citizens and because the richer the country is, the more it is likely to do to help others.
  4. Current campaigns to give reducing energy consumption a higher priority than other economies are mistaken.
  5. Almost all people like progress - considering that most migration is toward regions of greater progress.
Q. How could we be more sure that progress is sustainable?

A. There have always been people who regarded progress as illusory or unsustainable, although past doom-saying prophecies most often took a religious form. However, most people like progress and migrate toward parts of the world that are progressing.

Consider the argument above that we can use lower and lower grade ores when the present high grade ores run out and in the limit can use ordinary rock. No company or government is economically motivated to develop processes for using ordinary rock, because the supplies of better ores will last at least many hundreds of years and probably thousands. However, maybe some people would feel better about sustainability if processes for using ordinary rock had been developed.

Here are some possible studies that might give additional assurance and comfort to the worried. However, in so far as expectations of doom are a psychological or religious phenomenon, many people would react to the studies by thinking up additional menaces.

Here's a puzzle expressing my attitude towards many human problems. Look at THE DOCTOR'S DILEMMA

Here is a version of how ideologies affect people's attitude to various problems.

Here's a comment on "appropriate technology".

If you are at least partly convinced that human progress is sustainable, then take a look at the human future.. I think of the future in terms of opportunities rather than in terms of inevitabilities.

Here are some references.

Rupert Edwards disagrees with these pages.

Send comments to . I sometimes make changes suggested in them. - John McCarthy

These pages were begun on 1995 February 4.

The number of hits on this page since 1995 October 17th.

The free Web counter service says your visit is number . Let's see how its counts correspond to my own. Hmm. That's a substantial discrepancy in a short time.

In September 1998, all the hit counters got reset. I restored them but missed the hits between the crash and when I restored them.