Recent books and documentaries have made us aware of the danger of an environmental catastrophe if we do not halt and reverse some of our present practices and lifestyles. Catholic social documents as well have spoken of our God-given responsibility to take proper care of the world God has entrusted to us. At the same time there is another social phenomenon, less noticed because less dramatic, that represents grave consequences for the human race if it is not addressed. This is the growth of economic inequality.

Economists have long made the distinction between absolute poverty, which refers to those who lack the minimum requirements for physical survival, and relative poverty, which refers to those who lack the basic requirements for social survival. Relative poverty is sometimes referred to as inequality. What is becoming clearer is that this inequality is not only growing at a disturbing rate, but that its consequences are very serious for all people in any given society, and not only those directly affected.

Back in 1961 Pope John XXIII devoted the entire third section of his encyclical letter Mater et Magistra to the serious forms of inequality affecting today's world. Pope Paul VI, in his document The Development of Peoples spoke of "the scandal of glaring inequalities". Pope John Paul II several times expressed grave concern over the neglect of widespread inequality. Pope Benedict XVI, in his 2009 social encyclical Caritas in Veritate stated: "The world's wealth is growing in absolute terms, but inequalities are on the increase" (no. 22). He went on to point out: "Through the systemic increase of social inequality, both within a single country and between the populations of different countries (i.e. the massive increase in relative poverty), not only does social cohesion suffer, thereby placing democracy at risk, but so does the economy, through the progressive erosion of 'social capital': the network of relationships of trust, dependability, and respect for rules, all of which are indispensable for any form of civil coexistence" (no. 32). The pope's language is restrained but it suggests frightening consequences if we do not begin to reverse the present trend toward even greater economic inequality.

No too long ago the Canadian journalist Andrew Coyne - no wild-eyed radical - wrote: "There are consequences when societies develop an underclass, demoralized and falling out of contact with the mainstream . . . A poor family is not demoralized because it cannot afford a yacht, but because it cannot aspire even to the sorts of everyday things that average families take for granted."

A recent international bestselling book has now provided statistical evidence of the impact that inequality has on an entire society. Richard Wilkinson and Kate Pickett, both British medical researchers, have written The Spirit Level (London, Bloomsbury Press, 2010). The foreword to their book is a strong endorsement by the respected American economist Robert Reich. Commenting on the 2008 financial crisis, Wilkinson and Pickett state: "But the truth is that both the broken society and the broken economy resulted from the growth of inequality" (p. 5).

What Wilkinson and Pickett reveal through their careful statistical studies is that the entire society is adversely affected as economic inequality increases within it. For example, the higher the level of inequality in a society, the greater the amount of stress, and the greater the loss of self-esteem found across that entire society. As they move through their various studies they show that levels of social trust in a society are connected to income inequality; so too is the prevalence of mental illness, and so is drug addiction, as well as teenage pregnancy. Other studies show that as income inequality rises in a society, so too does violence.

At the beginning of Chapter 13, the authors state: "The last nine chapters have shown, among the rich developed countries and among the fifty states of the United States, that most of the important health and social problems of the rich world are more common in more unequal societies" (p. 173).

Because we believe in the dignity of every human being, Catholics understand that we must combat poverty wherever we find it. What is becoming clearer is that concern for the common good requires us also to do all we can, not only to fight against poverty but to reduce income inequality.