It can be a dangerous question, because some Catholics may ask the question in order to seek the "minimum" to believe, and the rest can be rejected outright, as if 180 degrees wrong. So I would caution against that motive and we can see why in a moment.
I would also say, from one angle, a Catholic doesn't have to believe any teachings the Pope declares. A Catholic doesn't even have to stay in the Church. He or she can walk away and reject the faith any time. I wouldn't recommend it. But simply being Catholic does not eliminate one's free will. But this essay will focus on believing the Pope while remaining a Catholic in communion with the Church.
Also, some do not understand why a Catholic would be perfectly reasonable in embracing the Church's teaching on abortion, but not a Pope's view on a socio-political situation. Hopefully, this essay will clarify that matter as well.
In Catholic teaching, it is believed the Pope exercises a charism of infallibility when, as a function of his office as St. Peter's successor, he defines a teaching of faith or morals for the whole Church to believe. (see CCC#888-892; Vatican I, 4.4.9; and prior discussion on Fallacies on Infallibility). This is not a reference to anything special about the Pope, who is, was, and always will be, a fallible mortal. This charism is a trust in God, who Catholics believe in Christ to have promised this divine assistance to the Apostles and their successors, especially Peter, i.e. the first Pope.
A PRECISE EXAMPLE
So when a Pope meets this criteria on a matter of faith or morals, yes, a Catholic is obligated to believe that teaching. There is no gray area. For example (in all subsequent quotes, bold emphasis is mine):
Accordingly, by the inspiration of the Holy Spirit, for the honor of the Holy and undivided Trinity, for the glory and adornment of the Virgin Mother of God, for the exaltation of the Catholic Faith, and for the furtherance of the Catholic religion, by the authority of Jesus Christ our Lord, of the Blessed Apostles Peter and Paul, and by our own: "We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful." (Pope Pius IX, Ineffabilis Deus)That Mary was preserved from original sin is not an "optional" teaching for the Catholic faithful. It is a defined matter. It is a matter of faith. And remember, the guarantee of this truth is the Holy Spirit. We believe the Pope's teaching on this matter because Christ promised to speak through his Church in such a way.
ASK IF IT'S A MATTER OF FAITH OR MORALS
Faith and morals are a good factor in identifying teachings that are representative of the Church versus an individual clergyman's opinion, even the Pope's, on a social or political or scientific matter. In fact, the Catechism teaches the following:
Divine assistance is also given to the successors of the apostles, teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a "definitive manner," they propose in the exercise of the ordinary Magisterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful "are to adhere to it with religious assent" which, though distinct from the assent of faith, is nonetheless an extension of it. (CCC#892)So you see how even matters taught by the Pope in non-definitive ways require a "religious assent," if that teaching is a matter of faith or morals. This is why it is imprudent to act as if a Pope's non-infallible statement is 180 degrees wrong. But the text does not say to offer religious assent if the Pope speaks on a matter of science, for example. Such matters are external to the Church's teaching authority. But keep in mind the rule of thumb to always look at a teaching and ask whether it falls under the category of faith or morals.
Now, let's look at less-defined propositions. In the Summer of 2015, Pope Francis stated:
Working for a just distribution of the fruits of the earth and human labor is not mere philanthropy. It is a moral obligation. For Christians, the responsibility is even greater: it is a commandment. (Pope Francis, Address at Expo Fair Santa Cruz de la Sierras, July 9, 2015)Quotes like these have been used by media to say the Pope condemns capitalism as a whole since capitalist societies produce many wealthy citizens. But if one examines the Pope's comment, the part that is a "moral obligation" is to strive for "just distribution" of goods. That is a very broad concept. In principle, the moral issue of justice (cf. CCC#1807) is obligatory for a Catholic to believe. Discussions of what government, social, political, or other solutions should prevail give rise to matters beyond the underlying moral issue.
In other words, a Catholic is not obligated to embrace nor reject "socialism," for example, as the solution to a problem of injustice. A Catholic is not required to embrace nor reject "capitalism" as a broad concept. Yes, a Catholic must oppose injustice, but methods of remedy are external to that moral crux. Even in that same speech, Pope Francis emphasized how the human person should be the focus when forming economies: "The first task is to put the economy at the service of peoples."
We can even see in the Pope's own words, for example, that capitalism, which he has often decried to the degree it does not serve people, still merits further understanding on his own part. On a plane ride from Paraguay to Rome, a reporter asked of his economic views: "This is perceived by Americans as a direct criticism of their system and their way of life." Pope Francis replied:
I heard that there were some criticisms from the United States. I heard about it, but I haven’t read about it, I haven’t had the time to study this well, because every criticism must be received, studied, and then dialogue must be ensue. ... Yes, I must begin studying these criticisms, no? And then dialogue a bit with this.Later in the interview, someone asked him about the economic situation in Greece. He conceded to not having had a good grasp on economics:
On Greece and the international system, I have a great allergy to economic things, because my father was an accountant and when he did not manage to finish his work at the factory, he brought the work home on Saturday and Sunday, with those books in those day where the titles were written in gothic. When I saw my father I had a great allergy and I didn’t understand it very well.So, you see in such an example, a Catholic can take the Pope's words and make a prudential examination to discover the parts that are religious (i.e. the concept of justice) versus parts that are economic or political (i.e. the U.S. economic system or the Greek economic system). Comments on religious concepts are in the scope of the Pope's teaching authority. Comments on economic concepts are not.
Let me approach this from one more angle. If you happen to read in the media that the Pope is against "income inequality," and thus pro-Socialism, one should not assume the Pope is endorsing any particular economic philosophy. Or, at least one should not assume what economic philosophy the Pope appears to endorse is a required belief for Catholics. We can deduce this with emphasis if we compare two quotes. On the plane ride just a couple days ago from Cuba to the U.S., Pope Francis said of his economic views:
I am sure that I have not said anything that is not present in the social Doctrine of the Church. ... My doctrine, on all of this, on Laudato Si, on economic imperialism and all of this, it is that of the social doctrine of the Church.And if we take a look at some of the Church's teaching on Socialism and income inequality in the past, we see such examples as:
It must be first of all recognized that the condition of things inherent in human affairs must be borne with, for it is impossible to reduce civil society to one dead level. Socialists may in that intent do their utmost, but all striving against nature is in vain. There naturally exist among mankind manifold differences of the most important kind; people differ in capacity, skill, health, strength; and unequal fortune is a necessary result of unequal condition. Such unequality is far from being disadvantageous either to individuals or to the community. Social and public life can only be maintained by means of various kinds of capacity for business and the playing of many parts; and each man, as a rule, chooses the part which suits his own peculiar domestic condition. (Pope Leo XIII, Rerum Novarum, 1891, #17)So here we see Pope Leo speaking how income inequality, per se, is not automatically an injustice. In fact, he says, a society needs the variation in order for business to have the capacity to function. And we have Pope Francis saying his teaching aligns with the Church's teaching. So where income inequality, for a Catholic, would become a concern, is where that inequality is the result of injustice.
The same can be said of the issue of "climate change," which appears frequently in the media, including with quotes from Pope Francis. (Note: An argument can be made that there is not scientific consensus on this matter either.) On this issue, the underlying moral principle is to have proper respect for creation (cf. CCC#2415), which is related to the commandment of "thou shall not kill." In Pope Francis' encyclical Laudatio Si, he acknowledges that he does not claim to teach a scientific solution to any ecological problems. He finishes with a caveat. He says on the ecology:
Finally, we need to acknowledge that different approaches and lines of thought have emerged regarding this situation and its possible solutions. ...there is no one path to a solution. ... On many concrete questions, the Church has no reason to offer a definitive opinion; she knows that honest debate must be encouraged among experts, while respecting divergent views.So on climate change, much as with economics, a Catholic only need give assent to the underlying moral issues relating to the 7th commandment on climate change and the matter of justice. The views a Catholic holds from there, with regard to ecological or economic systems, should be held with those moral principles in view.
Remember, when listening to a Pope's comments, one should examine the content to identify whether or not the comment is religious (i.e. a matter of faith or morals) or something else, such as economic, political, or scientific. If the Pope is teaching a principle of faith or morals, the Catholic's assent is required. If the Pope comment is about an economic or scientific matter, the Catholic's assent is not required insofar as any economic or scientific claims or solutions to problems. The Catholic needn't scruple over such things.
Dr. Anne Hendershott (an excellent speaker and writer on Catholic thought in this blogger's opinion) made the following statement recently:
I am a huge fan of Pope Francis because I actually read what he writes and it's wonderful. And he's so affirming and so loving. I'm not crazy when he talks about capitalism. I'm not crazy when he talks about climate change. But I don't really pay much attention to that stuff because that's not the non-negotiables. (Dr. Anne Hendershott, Professor of Sociology at Franciscan University, Sept. 2, 2015, on the Drew Mariani Radio Show (MP3))If a Catholic wishes to formulate an view on economic or scientific matters, that view should strive to satisfy moral principles of justice or the commandments where applicable. If one does this, he or she is already on the same page as the Pope and needn't worry about an explicit endorsement or condemnation of that view from the Pope.
The principle of faith and morals also should illuminate those who question Catholics who accept Church teaching on abortion (i.e. a moral matter) but not necessarily every Papal suggestion concerning climate change, income inequality, or other social, political, or scientific issues (i.e. not religious matters).