Christians know that we are part of the great family of God's children. Our deepest identity, that of children of the Father, makes us brothers and sisters to all men and women, created in God's image and likeness. And yet we are only too aware that fraternal relationships are not easy. Due to original sin, our dealings with one another are marked by the wound of the first fall. It destroys the harmony of interpersonal relationships as well as humanity's relationship with creation. Since the first pair of brothers mentioned in the Bible, Cain and Abel, and the elder's fratricide, there have always been family conflicts: Esau and Jacob fought over their birthright, Joseph was betrayed by his elder brothers, Moses suffered because of Aaron and Miriam...
The Gospels also show us siblings among the people close to Jesus: Peter and Andrew, James and John, and Mary, Martha and Lazarus. There, too, we find conflicts between siblings. They are present in the stories Jesus tells his listeners (when the prodigal son in the parable returns and his father throws a celebratory feast, the older brother is enraged and refuses to enter the house (cf. Lk 15:28)) and in the people around him (Teacher, tell my brother to share the inheritance with me (Lk 12:13); Lord, do you not care that my sister has left me by myself to do the serving? Tell her to help me (Lk 10:40)). However, Jesus has given human relationships a new dimension: Truly I tell you, whatever you did it to one of the least of these my brethren, you did it to me (Mt 25:40). He becomes one of us and identifies himself with the weakest of our brothers, with those who suffer and undergo injustice. Christians cannot be indifferent to others because we see in each of them something more than an equal: we see Christ himself. Becoming one of us, he identifies himself with the weakest of our fellow human beings, the one who suffers most, the one who suffers most injustice. No Christian can remain indifferent to another person, because in him he sees not only an equal, but Christ himself. "We must recognize Christ in each of these persons, and in each of them we have to see Jesus as our brother. By doing so it will be easier for us to serve them generously, attentively, affectionately, with peace and joy," St. Josemaría insists.
The first commandment
Pope Francis, commenting on the parable of the Good Samaritan, notes that it draws from an age-old problem: "Shortly after its account of the creation of the world and of man, the Bible takes up the issue of human relationships. Cain kills his brother Abel and then hears God ask: Where is your brother Abel? (Gen 4:9). His answer is one that we ourselves all too often give: Am I my brother's keeper? (ibid.). By the very question he asks, God leaves no room for an appeal to determinism or fatalism as a justification for our own indifference. Instead, he encourages us to create a different culture, in which we resolve our conflicts and care for one another."
If we were asked, we would probably say that we try to see Christ in strangers. But detachment from our brothers and sisters can occur subtly, in ordinary situations. Perhaps we criticize politicians we dislike the moment we see them on the news, distrust those who look and act differently, despise people in other socioeconomic spheres, and fight about sports or child-rearing. We might even judge other Christians because (rightly or wrongly) we do not think they behave as Christians.
We should not forget that Jesus tells the parable of the Good Samaritan when a teacher of the law, wanting to justify himself after a query about eternal life, asks, Who is my neighbour? His listeners already knew the answer to the original question because it was in the Torah: You shall love the Lord, your God, with all your heart, with all your being, with all your strength, and with all your mind, and your neighbour as yourself (Lk 10:27; cf. Deut 6:4 and Lev 19:18). Jesus goes a step further when he identifies the commandments: This is the greatest and the first commandment. The second is like it: You shall love your neighbour as yourself. The whole law and the prophets depend on these two commandments (Mt 22:38-40). At the end of the parable, when the teacher recognises that the proper attitude is that of one who has mercy on the wounded man, Jesus tells him: Go and do likewise.
Love your neighbour as yourself
In the New Testament, therefore, there is no doubt about what Jesus' followers are required to do. You have heard that it was said to your ancestors, 'You shall not kill; and whoever kills will be liable to judgment.' But I say to you, whoever is angry with his brother will be liable to judgment, and whoever says to his brother, 'Raqa,' will be answerable to the Sanhedrin, and whoever says, 'You fool,' will be liable to fiery Gehenna (Mt 5:21-22). Years after these teachings, John urged the early Christians to live fraternal charity as an indispensable part of love for God: If anyone says, 'I love God,' but hates his brother, he is a liar; for whoever does not love a brother whom he has seen cannot love God whom he has not seen (1 Jn 4:20).
We want to truly "see" our neighbour, as St. John says, recognizing Christ in him, especially in those who suffer. Sometimes we are the ones suffering and vulnerable, and sometimes we find others in pain: a homeless person we regularly pass on the street, a colleague who suffers ethnic or racial discrimination, an acquaintance with a degenerative illness or mobility problems that make life extraordinarily difficult, women whose professional or educational paths are blocked just because they are women, young people who go to class knowing they do not have the resources needed to complete their studies, friends addicted to pornography, gambling, or drugs... And the wars, famines, epidemics, and natural disasters that affect so many people.
Human dignity and Christian responsibility
Over the centuries, Christian values have spread through society and humanized it. Gradually we have learned to recognise that others have dignity, deserve to be treated with respect, and have rights equal to ours. Philosophy, sociology, and law, along with other disciplines, explore the value of human life and how to protect it, both individually and collectively. Progress in engineering, economics, and medicine have improved living conditions for much of the world's population, but new challenges are constantly emerging and much remains to be done.
People often accuse Christians of professing evangelical principles and shirking public action or using faith as a crutch so we can evade responsibility, as if prayer meant passivity and hope in eternal life led us to disengage from the world and the needy. Sometimes we perceive that many people accuse Christians of a lack of coherence between evangelical principles and public action, or consider that faith is a refuge that allows us to evade responsibilities. As if praying were synonymous with passivity, or hoping for eternal life would lead to disengagement from the world, forgetting those who need us. "Faith has untold power to inspire and sustain our respect for others, for believers come to know that God loves every man and woman with infinite love and 'thereby confers infinite dignity' upon all humanity. We likewise believe that Christ shed his blood for each of us and that no one is beyond the scope of his universal love. If we go to the ultimate source of that love which is the very life of the triune God, we encounter in the community of the three divine Persons the origin and perfect model of all life in society."
The world as an inheritance
The Prelate of Opus Dei frequently encourages us to feel the whole world and all it contains as something very much our own, as St. Paul taught: the world or life or death, or the present or the future: all belong to you, and you to Christ, and Christ to God (1 Cor 3:22-23).
"In the face of this reality – all things are yours – we rejoice in the joys of others; we enjoy all the good things that surround us, and we get involved in the challenges of our time. At the same time, we feel the world's situation deeply, particularly the sad reality of war and other situations of great need and suffering on the part of so many people, especially the weakest."
God has given us the world as an inheritance (cf. Psalm 2:8), so it is in our hands to transform it. We did not choose the time or place in which we live, but the circumstances that befall us are what God uses to help us bring what he gives us to fruition.
As Christians, we want Christlike hearts that feel others' needs as our own and lead us to act accordingly. This is a gift from God: "Fill the hearts of your faithful and kindle in them the fire of your love," we ask the Holy Spirit, for ourselves and for the whole Church. At the same time, "deeds are love, not sweet words," and Christians committed to God's love are necessarily Christians who actively seek to transform society, striving to conform it more closely to God's logic and love for humanity.
Personal and responsible
This commitment is shown, first of all, in constant, ardent prayer: the filial insistence of people asking for something good for those they love. "In prayer we too should be able to lay before God our labours, the suffering of certain situations, of certain days, the daily commitment to following him, to being Christian, and also the weight of the evil that we see within ourselves and around us, so that he may give us hope and make us feel his closeness and give us a little light on the path of life."
In addition to a commitment to presenting all our needs to God, transforming the world to make it more human, Christian, and divine, and showing the truth, goodness, and beauty of God's plan for our happiness is a duty of justice. Christians, working with others, invoke all the creativity of love in seeking new ways to make Christ's Gospel message a reality in our own circumstances, here and now.
This can be done in many ways, depending on the character of each place, time, and person, as well as our family and professional opportunities and our political, economic, and social preferences. "For by the very circumstance of their having been created," the Church teaches, "all things are endowed with their own stability, truth, goodness, proper laws and order. Man must respect these as he isolates them by the appropriate methods of the individual sciences or arts," and "all Christians must be aware of their own specific vocation within the political community. It is for them to give an example by their sense of responsibility and their service of the common good."
There are many ways of doing good. The Church encourages her children to act freely and with plurality, without imposing any particular school of thought. Inspired by the same ideal, Christians may come together in civil or religious associations or — more often — work in public or private initiatives meant to improve society without being run by Catholic institutions.
Charity "gives real substance to the personal relationship with God and with neighbour; it is the principle not only of micro-relationships (with friends, with family members or within small groups) but also of macro-relationships (social, economic and political ones)." 
That is why each person should look for ways to contribute to solving the social problems around them. St. Josemaría encouraged the people he spoke with to be responsible citizens, capable of transforming society and improving it through their work. "My children, each of us acts in a personal and responsible way."
Small gestures can do great good. Little by little, they shape our attitude toward others. A parent making time to listen to an adolescent child facilitates openness to dialogue with contemporary culture. A child learning to be attentive and affectionate to elderly grandparents discovers the value of the fragile and vulnerable. A colleague refusing to engage in workplace conversations that criticise or defame people who are not present fosters a culture of respect and trust. At other times, our capacity for transformation is rooted in our professional training or social position. At work or through civil and political action, we influence bills that make it easier for families to access necessary resources, denounce abuse and economic corruption, end practices that segregate certain people, and so on. Doctors, members of parliament, CEOs, and journalists can do their jobs well without "getting into trouble," but they can also choose to "complicate their lives" and contribute through their work to the construction of a fairer world.
The social doctrine of the Church in dialogue with the world
The Church proclaims moral principles in the social sphere when the fundamental rights of the human person or the salvation of souls are at stake. It was instituted by Christ to bring the message of salvation to all people and cannot stand idly by in the face of what is human. From the 19th century onwards, to help Christians act justly amid new economic, political, and social systems, the Church has established parameters to keep the Gospel message in view in changing circumstances. For this reason, the Compendium of the Social Doctrine of the Church contains some guiding principles.
The principle of the common good affirms the need for "social conditions which allow people, either as groups or as individuals, to reach their fulfillment more fully and more easily." The principle of the universal destination of goods reminds us that "created things [should] be shared fairly by all mankind under the guidance of justice tempered by charity." The principle of subsidiarity establishes that "all societies of a superior order must adopt attitudes of help ("subsidium") — therefore of support, promotion, development — with respect to lower-order societies" in order to care for "family, groups, associations, local territorial realities; [...] for that aggregate of economic, social, cultural, sports-oriented, recreational, professional and political expressions to which people spontaneously give life and which make it possible for them to achieve effective social growth."
The principle of participation comes from the principle of subsidiarity and "is expressed essentially in a series of activities by means of which the citizen [...] contributes to the cultural, economic, political and social life of the civil community to which he belongs. Participation is a duty to be fulfilled consciously by all, with responsibility and with a view to the common good." Finally, the principle of solidarity "requires that men and women of our day cultivate a greater awareness that they are debtors of the society of which they have become part. [...] A similar debt must be recognized in the various forms of social interaction."
These principles help us realise that many of the social initiatives flourishing around us are founded on shared values. Studying and making them known is an opportunity to work together with our fellow citizens and build a fairer society.
Truth, freedom, justice, and charity
The principles of the Church's social doctrine are based on four fundamental values: truth, freedom, justice, and love.
Love for our neighbour should drive Christian life, both personally and socially. "The Church must not only proclaim the word but must also put the word — which is charity and truth — into practice." The global crises of recent years have illustrated this: those who suffer are united in solidarity. Families come together when a loved one is ill, and neighbours start to interact more when they are forced to spend more time at home. But we can also choose these attitudes when they are not forced by circumstances: Do I know the names of the people in my apartment building, or in the farthest house in my town? Have I talked to each of them, taken an interest in their concerns, and sought to be close to them?
What may appear to be simple gestures of politeness or shows of kindness can in fact reflect God's love for every person: "Love, overflowing with small gestures of mutual care, is also civic and political, and it makes itself felt in every action that seeks to build a better world. For this reason, charity finds expression not only in close and intimate relationships but also in macro-relationships: social, economic and political." A coherent Christian's unity of life leads him to act with charity at every level, in issues that affect him or her directly and those that seem more distant.
With respect for everyone, and valuing the good of the person over their own idea or opinions, Christians can intervene in all kinds of questions: we act creatively and responsibly, without attributing our personal preferences to the Church. "As Christians, you enjoy the fullest freedom, with the consequent personal responsibility, to take part as you see fit in political, social or cultural affairs."
"If we love others with charity, then first of all we are just towards them. Not only is justice not extraneous to charity, not only is it not an alternative or parallel path to charity: justice is inseparable from charity, and intrinsic to it. Justice is the primary way of charity." And vice versa: the struggle for the common good will always be guided by understanding and respect. It would be nonsensical to seek justice with hardness of heart or to rejoice in something objectively wrong because it confirms our personal beliefs.
When a Christian sees people suffering the consequences of immoral actions or lifestyles or rectifying, turning to God, and beginning another way of life, the only possible response is affectionate understanding. We accompany others; we can never look down on others in self-satisfaction. Just as the Church dialogues with the world out of charity, so we, in the world, try to hold conversations open to all, seeking to include everyone without closing ourselves off to ideas we perceive as threats, welcoming different points of view and learning from others.
The apostles were not a uniform group. They came from different backgrounds and professions, their characters were sometimes incompatible, and they held opposing opinions... But they were united by their love for Christ and their mission of bringing the Good News to the world. Thus, combining the primacy of Peter and collegiality with their own identities, they fulfilled Christ's command: Go into the whole world and preach the Gospel to every creature (Mk 16:15).
The Lord's promise
The Christian obligation to love one's neighbour begins, like all our obligations, with God's love for humanity. He is the one who transforms hearts and renews the world: "Charity and justice are not only social but also spiritual actions, accomplished in the light of the Holy Spirit."
We know that we cannot achieve perfect justice on earth, and we look forward to the justice of eternal life. This never leads us to neglect our earthly duties, however, because we know that eternal life depends on our struggle to live out Jesus' "you did it to me" here on earth. We hope to transform the world, contribute to the happiness of those around us, and so be happy ourselves, because Jesus himself made us a promise: Blessed are those who hunger and thirst for righteousness, for they shall be satisfied (Mt 5:6).
 Cfr. Catechism of the Catholic Church, 400.
 St. Josemaría, Letter #3, 31.
 Pope Francis, Fratelli tutti, 57.
 Ibid, 85.
 Fernando Ocáriz, Letter 19.III.2020, 7.
 Alleluia, Solemnity of Pentecost (Cycle B).
 Pope Benedict XVI, General Audience, 1-II-2012.
 Second Vatican Council, Gaudium et Spes, 36.
 Ibid, 75.
 Pope Benedict XVI, Caritas in veritate, 2.
 St. Josemaría, Letter #3, 37.
 Cfr. Catechism of the Catholic Church, 2032; 2420.
 Compendium of the Social Doctrine of the Church, 186.
 Cfr. ibid, 171.
 Ibid, 186.
 Ibid, 185.
 Ibid, 189.
 Ibid, 195.
 Pope Benedict XVI, General Audience, 25-IV-2012.
 Pope Francis, Fratelli tutti, 181.
 St. Josemaría, Friends of God, 11.
 Pope Benedict XVI, Caritas in veritate, 6.
 Pope Benedict XVI, General Audience, 25-IV-2012.