A primer on Pope Francis' politics

When CBS News' Scott Pelley asked Pope Francis whether he plans to address issues like immigration in America this week, the pope answered, "I shall talk about what the Holy Spirit shall inspire me to say."

While the pope's visit is first and foremost a spiritual one, his words and actions this week will surely have some political influence. The pope is, after all, the head of a sovereign state (albeit a small one) and will be the first pope ever to address the U.S. Congress. And as head of the Catholic Church, the pope stakes out the church's positions on issues morality collides with public policy -- that covers everything from abortion and marriage to climate change and poverty.

Some liberals have praised this pope for taking the church's focus off of issues like marriage and abortion. Conservatives, meanwhile, are mindful that a shift in tone and focus doesn't mean the pope is changing church dogma.

With that in mind, here's a refresher on what Pope Francis has said on some key political issues:

Abortion

Pope Francis made headlines earlier this month when he announced that, for a temporary period starting later this year, it will be easier for women to receive absolution for the sin of abortion.

Specifically, under the pope's decree, any priest can absolve a woman for the sin of abortion from December 8, 2015 to November 20, 2016, during what's known as the Jubilee year of Mercy. Francis wrote in a letter to Archbishop Rino Fisichella, head of Jubilee initiatives, "I am well aware of the pressure that has led them to this decision. I know that it is an existential and moral ordeal."

The decree aligns with Francis' remarks early in his papacy that the church needs to "to find a new balance" that puts less focus on issues like marriage and abortion, or risk driving the faithful away.

Even so, Roman Catholic canon law still considers abortion a "reserved sin." That means that having an abortion results in automatic excommunication -- banning a person from all Catholic sacraments. Under normal circumstances, only bishops are allowed to absolve a woman for the sin of abortion.

And while Francis is sympathetic to the moral questions women face about abortion, he has still spoken out critically about it. Last year, he called sanctioned abortion evidence of a "throwaway culture" that poses a threat to world peace.

Marriage, sexuality

In keeping with his promise to take the church's focus off of issues like sexuality and abortion, Pope Francis in 2013 told reporters that "you can't marginalize" people because of their sexual orientation. "If someone is gay and he searches for the Lord and has good will, who am I to judge?" he said.

The pope has reiterated that point of view -- but he hasn't backed away from the Catholic Church's teachings about marriage. In January of this year, he told a crowd in the Philippines that the traditional family was being "threatened by growing efforts on the part of some to redefine the very institution of marriage." A Vatican spokesman confirmed the pope's words did refer, at least in part, to gay marriage advocacy. Meanwhile, in May, the Vatican called the Irish public's vote legalizing same-sex marriage "a defeat for humanity."

Pope Francis has also weighed in on the unions of heterosexual couples. Earlier this month, he announced changes to the Catholic marriage annulment process, making it faster, easier and less expensive. "People who started a new union after the defeat of their sacramental marriage are not at all excommunicated, and they absolutely must not be treated that way," Francis said a month prior.

Climate change

Earlier this year, Pope Francis issued a 184-page encyclical -- the most authoritative teaching document the pope can issue -- on climate change. While past popes have stressed the importance of environmental stewardship, Francis' focus on the subject is unprecedented -- which is perhaps to be expected from a pope who took his name from St. Francis of Assisi, the patron saint of animals and the environment.

The encyclical was decidedly political. It declared that global warming is "mostly" due to human activity and the burning of fossil fuels, and that it is a problem that disproportionately impacts the poor. Francis blamed the problem on a "structurally perverse" economic system where the rich exploit the poor, turning Earth into an "immense pile of filth."

• Catholic Republican congressman will boycott Pope Francis' address

"It is not enough to balance, in the medium term, the protection of nature with financial gain, or the preservation of the environment with progress," he wrote. "Halfway measures simply delay the inevitable disaster. Put simply, it is a matter of redefining our notion of progress."

The pope isn't just talking about climate change but also actively working to mobilize local leaders on the issue. After Francis issued the encyclical, the Vatican held a two-day conference on the climate change, bringing about 60 mayors from around the world to Vatican City to discuss ways to address the problem.

Francis has clearly irked some conservatives, who say the pope's encyclical is too political. At least one conservative congressman, Rep. Paul Gosar, is boycotting Pope Francis' historic address before a joint session of Congress on Thursday because of the pope's stance on climate change. The pope also plans to address climate change at the United Nations when he's in New York on Friday.

Poverty, income inequality

Pope Francis has made it quite clear that he believes capitalist systems keep poor nations and people under the thumb of the rich. In his climate change encyclical, he slammed the "structurally perverse" economic systems that let the rich exploit the poor.

In a speech in Bolivia in July, Francis warned that "colonialism, both old and new... reduces poor countries to mere providers of raw material and cheap labor, engenders violence, poverty, forced migrations and all the evils which go hand in hand with these." He added that "new colonialism" is a threat that takes many forms: "At times it appears as the anonymous influence of mammon: corporations, loan agencies, certain 'free trade' treaties, and the imposition of measures of 'austerity' which always tighten the belt of workers and the poor," he said, according to a transcript from the Vatican.

In 2013, he told Vatican ambassadors that growing income inequality is leading to "a new, invisible and at times virtual, tyranny.

Rejecting the trappings of consumerism, Francis has appealed to people to live simply and does so himself. Rather than live in the Apostolic Palace, the official residence of the pope, Francis has opted to live in the more modest Vatican hotel. He also takes time to meet with the poor. After he addresses Congress on Thursday, Pope Francis plans to meet with a group of homeless people in Washington, D.C.

Immigration

Pope Francis has repeatedly stressed the plight of migrants, including those crossing over the U.S.-Mexico border.

Earlier this year, Francis responded to a group of Arizona high school students, who wrote to him about the immigrants they assist at the southern border. In his letter back to the students, the pope thanked them for sharing the story of those "who live daily the immigration phenomenon that generates all sorts of inhumane consequences."

Immigration will be a key focal point in the pope's tour of the U.S. On Friday, he'll meet with immigrant families at a school in New York City. On Saturday, he'll deliver a major speech focusing largely on immigration in Philadelphia. To ensure there is a diverse audience, tickets are being distributed to Philadelphia parishes with large immigrant communities.

Meanwhile, in his address to Congress on Thursday, a senior Vatican official told CBS News' Anna Matranga, the pope "will talk about the vision of the pioneers who created the new nation of the United States, principles like religious freedom and open arms to immigrants. He will definitely encourage being open to immigrants."

Pope Francis has also urged Europeans to "renew their praiseworthy commitment of solidarity" toward migrants.