Once upon a time, money was scarce and the temptation to hoard it (as in the fairy tales of misers "in their counting houses counting up their money"), depriving others of its use, was powerful. For that reason, Christian preachers used to inveigh against wealth and "materialism"--and many still preach the same sermons today. They do not realize that times have changed, and nearly all of today's wealth, far from being hoarded, is turned over to society in the form of investments that fuel creativity. Nowadays, money is far more tightly related to matters of the spirit than we usually recognize.

Before modern times, misers were universally regarded as villainous, and avarice seemed to be a particularly vicious sin against the whole society. It did not harm merely the miser, as overeating harmed the glutton; it hurt all those into whose lives it brought deprivation. In those days, wealth implied a zero-sum game. If one person had all, others had zero. Many of the parables of Jesus remind us that in wealth of this sort lies no real security or peace or virtue.

In premodern times, money was almost entirely a medium of exchange. It had very little role as investment capital, that is, as a social instrument for the creation of new wealth for the whole society through sustained invention and discovery. In short, the role of money as an instrument of the creative human mind did not really emerge until modern times, at least in sufficient density to lend a new character to the era. Until that happened, the only real way for a king or a baron or even a brigand to acquire new wealth was to mount up an army and go seize it. No one knew how to create wealth, only how to take it.

The Biblical adage "the love of money is the root of all evil" aptly described the behavior of the powerful as the peasants and yeoman of ancient and medieval times saw--and experienced--it, having often been the victims of plunder, war, and rapine.

Not until 1776, when Adam Smith published his "Wealth of Nations," did any major thinker raise the question of wealth in a systematic and practical way, with an eye toward shifting the world's attention from warfare to investment, from the taking of existing wealth to the creation of new wealth. The conventional wisdom held that nothing at all--except alms--could be done to alter the permanent condition of the poor. "The poor ye shall always have with you," as Jesus said. It was Adam Smith's dream to understand the causes of wealth so that new wealth could be created in a sustained and systematic way until every last person on earth was lifted out of poverty.

Pope John Paul II's economic and social encyclical "Centesimus Annus" reflects this insight. The pope points out that whereas in the ancient world, land was the most important form of wealth, in our time invention, discovery, knowledge, and know-how have become the new causes of the wealth of nations, "and the wealth of the developed world is mainly of this sort," John Paul writes. This is not capital in the Marxist sense of brute machinery, but capital in the sense of human skill, knowledge, and innovation that is the main generator of wealth today. In short, human capital.

It is instructive to note that the stock figure of the miser in novels, short stories, and fables has virtually disappeared in contemporary times. Why is this? In the old days, when money had virtually no creative use as investment for innovation and discovery, anyone who hoarded money was a villain, subtracting financial liquidity from the scarce public store. Today, such a person--piling up his money in an attic strongroom--would be less a villain than a fool. What good is money that is sitting still?

A wise man would invest it in a reasonable, safe, creative project and perhaps use a smaller portion of his expendable resources in riskier projects that may or may not work out but promise larger rewards if they do. Today, for example, there are all sorts of investment opportunities: in fiber optics, cellular and satellite technologies, Internet services, revolutionary software, and smaller, swifter, and more-efficient computer hardware. Money, in the sense of investment capital, is a new handmaiden of the creative human spirit, enabling human capital to flourish.

One consequence of this transformation is that today we see more clearly than ever that the most important resource in any nation is the creative minds of its citizens. This resource is not only renewable but, as Aristotle said, in some sense without limit: The mind is open, questing, always probing and asking questions.

This insight transforms arguments about population control.

It is false that crowded or "overpopulated" countries must be poor, and underpopulated countries are more likely to be rich. In fact, some of the most densely populated regions of the world--Japan, the Netherlands--are among the wealthiest. The main cause of wealth is the training and organization of the human mind.