A version of this article appeared in The Commentator May 6, 2012.

Most arguments against open-ended population growth are derivatives of the argument from personal incredulity: I cannot imagine how it could be so, therefore it cannot be. Could the earth really support 10, 20, 30 billion people?

Alarmists’ arguments, however dressed up in statistics and presented with a veneer of scientific authority, always rely on this intuitive skepticism. Their flaw is that they do not understand what drives prosperity.

We will run out of road eventually–won’t we?

The basis for this intuition is easy to follow: all resources are limited; add up the total quantity of resources; divide by the rate of consumption; the result, obviously, is the end of civilization. Every day that people go on producing things and making babies just brings us that much closer to Armageddon.

In this view, we are just marking time as production destroys the planet; the arc of history bends towards annihilation. We can only hope to delay judgment day, but we cannot postpone it indefinitely. The most optimistic of outlooks under this scenario relies on imposing universal austerity and an imperative to cannibalize all human waste products (also known as “recycling”), until the global economy becomes a futile hamster wheel, where material progress would only mean bringing us closer to our final reckoning.

Striking a less apocalyptic note than their ideological cousins on the left, opponents of open borders also rely on this intuition of finiteness. Foes of immigration loudly insist that immigrants “take Americans’ jobs.” Enemies of free trade cry that outsourcing “sends American jobs overseas.” Both restrictive immigration and protectionist trade policies are based on the flawed idea that the number of “jobs” in the economy is fixed and that more workers means dividing the same amount of “work” between more people, meaning either higher unemployment or lower wages. The more moderate restrictionists argue that we just cannot “afford” too much immigration right now, and that we must choke off the flow of immigrants until the economy can “sustain” the influx of workers.

The reason why our intuition about the “limits to growth” is so wrong is that it fails to comprehend the role of human ingenuity in shaping and harnessing the environment. More people in a global market economy means more minds working to solving problems, more people producing things for each other, and more knowledge and ideas available to everyone. Growth is only limited by our ability to innovate and solve problems, and that is only limited by our access to innovators and problem solvers.

The quixotic effort to quantify the exact amount of resources on earth and calculate when we will “run out” is doomed to fail because people are constantly inventing new ideas and discovering new uses for things. Nothing is a resource until someone discovers an application for it.

The reservoir of liquid petroleum buried in the Arabian sands was not a resource before someone discovered a use for oil, just as the tar sands of Canada were not until someone discovered how to extract a usable substance from them. “Natural” resources are not fixed because resources are not found in nature–they are created by the human mind.

Efforts to extrapolate when our supply of resources will fail do not to take into account how human resourcefulness and economic incentives cause markets to shift and evolve. Alarmists like Paul Ehrlich and Jon Holdren worry that “if things go on as they are,” disaster will result–ignoring the most salient feature of free markets: things never go on as they are. Creative destruction and market adaptation are continuously changing the game.

The origin of the wealth of nations

Anti-immigration and anti-population growth rhetoric are both based on the flawed perception that wealth is divided, not created. If there were half as many people in the United States today we would not all be twice as rich. Indeed, it is likely that we should all be less than half as wealthy as we are now, for 300 million minds working for each other are capable of producing more than twice as much wealth as 150 million minds. Our collective intelligence, industry, and output falls when we limit our access to further human capital.

Our prosperity depends on protecting individuals’ freedom of association. Connections between and among people and industries are what drive the profligate recombination and evolution of ideas that is critical to economic growth. If America’s population declined by two-thirds, we would not merely stagnate, we would regress. In a country limited to only 100 million minds, how many industries, technologies, and conveniences of modern America would we have to give up? Then ask yourself, how many new ideas, new innovations, and new solutions would we forego ever having by arbitrarily limiting population growth? How many would we lose by cutting ourselves off from world by closing our ports and borders?

The continued success of our nation and our species depends on tapping the bottomless well of ingenuity and invention that is the only genuinely natural resource: the human mind. The lives of billions depend on not cutting ourselves off from each other and allowing the free association of people and ideas to flourish. We must embrace a world in which the potential for trade, migration, and growth is truly open-ended.