We welcome Pope Francis to the United States and look forward to his address today to a joint session of Congress. His message of mercy and aiding the poor, especially migrants, is much needed in today's world. And he has spoken eloquently about reducing pollution.

We would like to add a few thoughts to his considerations, keeping in mind his call in his May encyclical, "Laudato Si," "I urgently appeal, then, for a new dialogue about how we are shaping the future of our planet."

Like the clergy of all major faiths, Pope Francis decries materialism, greed and the idolatry of money. He has branded the "unfettered pursuit of money" the "dung of the devil."

On his way to our country, Pope Francis visited Cuba. He met with Fidel Castro and his brother, Raul, whose socialist regime for more than five decades basically has banned profits, except for small shops. During that time, Cuba went from being the most prosperous country in Latin America to one of the poorest.

Meanwhile, Cubans seeking freedom fled to the United States, with many achieving prosperity, including the families of two presidential candidates, Sens. Marco Rubio and Ted Cruz.

On Yale University's Environmental Performance Index, Cuba ranked 64th among nations, with an overall EPI score of 55 (out of 100). By contrast, the top countries were those that also placed highest on free-market rankings: Switzerland (EPI: 88), Luxembourg (83) and Australia (82).

Worse, on "Trend in Carbon Intensity" — a major concern of Pope Francis, who seeks to reduce and eliminate carbon use — socialist Cuba scored 0.0 (out of 100), the lowest possible. The anti-profit country isn't doing anything at all. Rich Switzerland scored 68.

The evidence confirms that only free markets can develop technologies that both cut pollution and lift up the poor. Clergy need to caution against avarice. But as was written just after the fall of the Berlin Wall by Pope John Paul II, whom Pope Francis proclaimed a saint in 2014, "(T)he free market is the most efficient instrument for utilizing resources and effectively responding to needs."

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