Pope Francis's encyclical On Care For Our Common Home is significant as a strong and unqualified declaration of the need for humankind to change course if it is to avoid calamitous physical degradation of the only planet it has as a home. Although the Roman Catholic pope lacks, as Stalin reminded us, any army divisions with which to exert his influence, he does have one of the most credible claims to worldwide moral authority. This week he is using that authority to tell the world that the environmental calamity of which he writes is, to quote from the encyclical, “one of the principal challenges facing humanity in our day.”

The encyclical is in some respects an oddly heterogeneous read, which intersperses theology between sections that sound more like the products of a think tank, a nerdy advocacy group, or a philosophical discussion group. The document is sprinkled with terms such as anthropocentrism and techno-economic paradigm. The encyclical addresses multiple aspects of the environmental damage that is despoiling our “common home,” but its single most important theme is acceptance of the mountain of scientific evidence that human activity is heating the planet, and the consequent need to change the direction of that activity.

The encyclical also is blunt and perceptive in describing the reasons for resistance to that message. “Many of those who possess more resources or economic or political power,” says Francis, “seem mostly to be concerned with masking the problems or concealing their symptoms...” The document further observes, “There are too many special interests, and economic interests easily end up trumping the common good and manipulating information so that their own plans will not be affected.”

That is a good analysis of what underlies some of the resistant reaction to the encyclical, including from some American politicians who belong to the church that Francis heads. That includes Jeb Bush, who earlier this month was the sole Republican presidential candidate invited to speak at a golf and fishing retreat hosted by the coal industry, which is one of the most prominent of the special interests opposing action on global warming. Reacting to the papal encyclical, Bush said, “I don't get economic policy from my bishops or my cardinal or my pope.” Bush continued, “I think religion ought to be about making us better as people and less about things that end up getting in the political realm.” Bush did not appear to have qualms as governor of Florida about taking guidance from his church on things that get in the political realm; he often cited church teachings as a guide for public policy on matters such as abortion.

Even more prominent inconsistencies of that sort come from fellow Catholic and an avowedly Christianist politician, Rick Santorum, who said about the encyclical, “The church has gotten it wrong a few times on science, and I think that we probably are better off leaving science to the scientists...” Pope Francis, of course, far from trying to have the church make scientific pronouncements, was instead deferring to the overwhelming scientific consensus about global climate change and the reasons for it. Leaving science to the scientists is exactly what he is doing in the encyclical. This is much more respectful of Enlightment values and the scientific method than either outright climate change denial or the usual tactic of resistant American politicians who, realizing the stupidity of such denial, still try to cast doubt on the scientific consensus with a pseudo-agnostic "I'm not a scientist" tactic.

When it comes to being guided by teachings from the Holy See (on matters other than climate change), one of Santorum's most direct pronouncements, uttered during the 2012 presidential campaign, was a comment about John F. Kennedy's assurance a half century earlier that if he were elected president he would not impose his Catholic faith on the nation. Kennedy's reassuring statement about separation of church and state, said Santorum, made him “want to throw up.”

Now in response to publication of the new encyclical, Santorum says the church should focus on what it's “really good at, which is theology and morality.” Well, there certainly is a lot of both theology and morality in the encyclical. Francis frames global warming and other environmental degradation as a moral issue along two chief dimensions. One is rich versus poor, with the former's economic interests and political clout impeding action to correct environmental destruction that makes the poor suffer at least as much as anyone else. The other dimension involves the current generation versus future generations. The encyclical has a section titled “Justice Between the Generations.” It is wrong, says Francis, for the current generation, with a narrow focus on its own immediate economic interests, to ruin the planet on which future generations must live. That is a moral issue, as well as an economic issue and a political issue. Politicians must be made to confront the subject on all of those levels.