The Catholic Church has two main creeds: the longer Nicene Creed and the shorter Apostles' Creed. The Apostles' Creed mentions "the communion of saints", which refers to how the Church is the mystical Body of Christ, whose life is the Spirit, flowing like blood and enabling the baptized to help each other. The members of this Body also include the saints in heaven too, who care for and pray for us. We can also pray for the souls in Purgatory and help them enter Heaven earlier. Our communion with other humans reflects the communion enjoyed by the Three Persons of the Trinity. Traditionally, the Church comprises of three parts: the souls in Heaven, known as the Church Triumphant; the souls in Purgatory, known as the Church Suffering; and the souls on Earth, known as the Church Militant. Furthermore, there are three categories of saints: Biblical, Traditional, and Ecclesiastical saints.

The third mark of the Church is its catholicity, a term that means "universal". Since the Catholic Church must endure until the end of the ages and proclaim the Gospel to all nations, the Church welcomes everyone, whether poor or rich, educated or uneducated, people from different ethnicities. As a result, the Catholic Church translates catechism texts in different languages and sends missionaries around the world. In the past, agricultural societies were largely illiterate, so old European churches are filled with stained glass instead. The fourth mark is its apostolicity; the priests and bishops of the Church are consecrated by preceding bishops. And if we read the Church fathers, people are often surprised to find that the early Church worshipped much in the same way as the Catholic Church today.

The Church is “one, holy, catholic, and apostolic” – these are her four marks. She is one because she is led by the same Pope, believes in the same doctrine, and celebrates the same Sacraments. She is holy because her founder is Christ and her Pope is Christ’s Vicar on earth, teaches doctrine to sanctify people, and provides the means for people to become saints. The Church is, in a sense, a hospital: we are patients who can get better if we obediently listen to the doctors’ advice. But no one can force us – we have the freedom to disobey and hamper our recovery. In the Church, we see many faithful who have refused to live like Christ but also many who have, the saints. These lives of faithful witness show in a visible way the holiness of the Church.

The writers of the Bible could not write errors into the Bible because they wrote under the inspiration of God. But outside of writing the Bible, the writers could sin, make mistakes, even write errors. The Popes are the same – there were many saintly Popes and many criminal Popes. But in deciding matters of faith and reason, God guarantees that they will not err. The teachings of Christ are transmitted to us through the written Scriptures and the oral Tradition. The Church also teaches through the Magisterium: the Pope with his bishops make a final decision in cases of disagreement on faith and morals. These infallible decisions must have four conditions: (1) it must be related to faith or morals, (2) the Pope must proclaim it in his capacity as Pope, (3) it must be proclaimed to the entire Church, and (4) the Pope must make his intention clear. The infallibility of the Pope is not to make his person infallible but is meant to help him serve the Church and preserve the true faith.

The Catholic Church has three defining characteristics: authority, infallibility, and indefeasibility. Since she continues Christ's mission as prophet, priest, and king, she inherits His authority to preach, serve the Sacraments, and set moral laws. Just as countries have the authority to set secular laws to maintain the peace and enforce them with police, the Church sets spiritual laws for the salvation of souls and enforces them with the force of personal conscience. The Church has different kinds of laws: canon law is promulgated by the Pope himself, while diocesan law by the local bishop. The Church's infallibility does not mean the Pope cannot err in all things, but that his teaching on faith and morals will always be correct. Throughout history, countries and ideologies have risen and fallen, but Jesus promised that the demonic powers would never defeat the Church - she alone will endure until the end of time. In her first century, the Church suffered external persecutions, then she suffered internal heresies, but she has always endured through the help of saints who encouraged people to stay close to God.

On the fiftieth day after Easter, we celebrate Pentecost, the day the Holy Spirit descended and the birthday of the Church. The Church is the body of Christ, with the Virgin Mary as the neck, connecting us to the head of Christ, and the Holy Spirit as the soul. The Church continues the work of Christ on earth, bringing people to eternal life in heaven. Christ had a threefold mission: as prophet, priest, and king. The Church prophesizes by teaching the Gospel to all nations, acts as priest by offering up worship and sanctifies the people through the Sacraments, and leads people to do good and avoid evil.

When the Holy Spirit descended on the Apostles forty days after the Resurrection, they were filled with understanding of the Gospel, love, and hope. Immediately, they headed outside and began proclaiming the Gospel to people of different languages. The Sacrament of Baptism is heavily related to the death and resurrection of Christ – it symbolizes death to sin, life in Christ. The Sacrament of Confirmation is heavily related to the descent of the Holy Spirit – the Holy Spirit dwells in the recipient and illuminates their reason and will to do good. To open our hearts is the best attitude we can have to honour the Holy Spirit. St. John Paul II especially honoured the Holy Spirit, in 1983 he beatified Sr. Mariam Baourdy, who was also devoted to the Holy Spirit and brought a message to Pope Pius IX that the priests and seminarians had neglected their devotion to the Holy Spirit.

The Apostles Creed proclaims that when Jesus died, His body was buried and His soul entered Hell. Hell in this case refers to the place of souls not in Heaven, not the place of damned souls. One part of this “Hell” is Purgatory, another is called the “Limbo of the Patriarchs” or the “Bosom of Abraham” – the place where virtuous souls like Adam and Eve, Moses, and David waited for Jesus to open the doors of Heaven for them. After Jesus rose from the dead, He waited on earth for 40 days to prove His Resurrection and provide instruction to His disciples. Before Jesus ascended into Heaven, He gave them a threefold mission: (1) to “make disciples of all nations” as prophets, (2) to baptize all people as priests, and (3) to lead all believers to salvation as kings. After Jesus ascended, He was seated at the right hand of the Father to show the completion of His salvific mission. His Ascension had three benefits for us: (1) it opened the doors of Heaven, (2) it permitted the descent of the Holy Spirit, and (3) it allowed Him to constantly pray for us before the Father.

Jesus’ Passion achieved a fitting sacrifice to God and gave us humans salvation. Why did Jesus have to become man and die? To give us life. But why did Jesus have to save us by the Cross? God didn’t have to use the Cross, but He found it fitting. From the Cross, we can learn God’s love, the horror of sin, and how to accept suffering. God shows us love through the language of sacrifice; by taking on the consequences of sin, we are reminded not to take Jesus’s sacrifice lightly; Jesus’ sacrifice gives meaning to our sufferings and allows us to join them with His sufferings. Jesus saved us by His Passion, death, and Resurrection – as God, His sacrifice has infinite value; as man, He truly represents us. Jesus is victorious over death and sin – these are inseparable.

During the first 30 years of His life, Jesus lived a life of labour, prayer, and service – there are two lessons we can learn from this. First, the value of a human life comes from God, not from other humans. Second, those working in ministry must be formed in silence and prayer. Catechesis is formed by doctrine, moral education, and worship of God. For doctrine, Jesus taught us the greatest mystery of all – that of the Holy Trinity and that salvation lies in the Catholic Church. For moral education, Jesus gave us the Eight Beatitudes to teach us sacrificial love and guide us to the Kingdom of Heaven. In worship of God, Jesus taught us the Lord’s Prayer, established the Seven Sacraments, and taught us to pray with confidence. Jesus used parables to teach us; these are of three types: (1) those about the Kingdom of God, (2) those about the mercy of God, (3) those about charity. Apart from words, Jesus also used miracles to prove the truth of His teachings – He exorcised demons 7 times, defied nature 10 times, healed the sick 15 times, and raised the dead 3 times. He also predicted His Passion and Resurrection, and predicted the fates of His disciples and Jerusalem.

A writer once wrote that there are two reasons why God waited for so long to send His Messiah. Firstly, humans sinned out of pride so the long wait served to humble them. Secondly, just as the first Adam’s creation was preceded by the wondrous creation of lesser creatures, the arrival of Jesus, the second Adam, was preceded by the many miracles of the Old Testament. The Old Testament can be divided into four parts: from Adam to Moses, from Moses to David, from David to the Babylonian Exile, and from the Babylonian Exile to Jesus. In the first period, the religion was primitive and led by the head of each family. In the second, Mosaic Law promulgated eternal law in the Ten Commandments and the temporary law for the Jews. In the third, King David combined religion and politics and his son Solomon built the Temple. In the last period, the Israelites were conquered by the Babylonians. The Son of God was the only person able to choose His mother. In order for her to be above the unfallen angels and to be fit to have authority over Jesus, she had to be without sin. God prepared the people of Israel for Jesus through the Old Testament, and He prepared Mary to receive Jesus’ birth.

Due to the fall of Adam and Eve, we have lost the supernatural gifts we would’ve inherited. Now, we must obtain them again from Jesus. But whereas Original Sin resulted from Adam and Eve’s actions, Actual or Personal Sin result from our own actions. Actual sin can be either mortal or venial. Mortal sin destroys our friendship with God and erases our previous merits; it has three conditions: (1) it must be a grave matter, (2) the sinner must be aware of its severity, and (3) the sinner must willingly assent to the sin. Mortal sin is the death of the soul, venial sin is the sickness of the soul. Venial sin is any sin that does not meet the three requirements to be a mortal sin. It weakens our intellect and will, reducing our resistance to temptation. Confession is mandatory for mortal sin, but only commendable for venial sin. If the soul has died, who else but God can bring it back to life? Apart from sanctifying grace, God also gives us actual grace to help us in our everyday life to do good and avoid evil. We cannot rely on our own strength but cooperate with God’s help to obey the commandments.

All men and women are the descendants of Adam and Eve. In the beginning, God placed our first parents in the Garden of Eden and gave them both supernatural grace and preternatural gifts. But after the Fall, Adam and Eve lost them and we as their descendants no longer inherit them at our birth, a state called Original Sin. We no longer have superior intellects to understand reality, our wills are biased towards our passions, and we can suffer and die. But whereas angels cannot repent after sinning, humans can still return to God through repentance. The demons must have been greatly enraged to know that Adam and Eve could still return to God after falling once. Just as the original Adam and Eve made humanity lose God’s grace, the new Adam and Eve—Jesus and Mary—returned humanity back to God's grace.

Once, a catechism teacher asked their students, “Who created the angels?” “God,” replied the students. “Then who created the devils?” The students thought for a long time until one of them said, “God created them as angels, but they turned themselves into devils.” Humans and the angels are esteemed above the rest of God’s creation. Angels are pure spirit and have no bodies but have intellect and will. The ones who refused God became devils. Many theologians speculate that these devils rebelled upon being told that the Son would become a man instead of an angel and that they would have to serve the God-man, Jesus. Lucifer was one rebellious angel who led other angels against God and became Satan. These angels, instead of glowing from their gazing at God, grew dim from gazing at themselves. We all have a guardian angel who protect us from evil and inspire us to do good – so we must honour their presence. Devils often attack us through temptation, but there are three ways to combat this: (1) to pray humbly in the name of Jesus and Mary, (2) to frequent the Sacraments and use sacramentals, and (3) to look down on devils.

God’s Revelation comes to us in natural and supernatural ways. His natural revelation is given to even those without religious training. Through created things, we can see God’s wisdom and goodness. And our hearts have irrepressible consciences which guide us to heaven. They do not come from our parents and teachers, but from God. Our hearts also possess a desire for perfect goodness and eternal happiness that only God can satisfy. God’s supernatural revelation comes from the Scriptures (the written Word of God), Tradition (the unwritten Word of God), and the Magisterium (the authority to interpret Scripture and Tradition). The Scriptures were written by human writers under the inspiration of God. Tradition was passed down by word of mouth from Jesus and the Holy Spirit to the disciples without being written down. The Protestants believe solely in the Scriptures even though certain doctrines, like the Trinity, are not explicitly stated there. The Orthodox accept Scripture and Tradition, but only the Catholic Church has the Magisterium, or authority to infallibly interpret the Scriptures and Tradition.

In the Creed, we profess our belief in the Holy Trinity: Father, Son, and Holy Spirit. God revealed Himself as one God in the Pentateuch of the Old Testament, and as three Persons in the New Testament. The word “nature” answers “what are you?”; the word “person” answers “who are you?”. What is the Holy Trinity? God. Who is the Holy Trinity? Father, Son, and Holy Spirit. Every spirit has the capacity to understand and love and God is pure spirit. The Father begot His understanding as His Son and their mutual love became the Holy Spirit. These two acts are eternal and why all three Persons of the Trinity have always existed. St. Augustine was once perplexed by pondering this mystery and saw a child scooping the seawater into a hole at the beach, so he said to him, “There is so much water in the ocean. How can you fit it in the hole?” The child replied, “How about you? Do you think you can fit the Holy Trinity in your limited mind?” Because God is not solitary, He is the source of all human organizations: families, countries, and the Church. In all these, when we act with self-giving love, we reflect the inner life of God.

“I believe in one God, the Father almighty, maker of heaven and earth.” Time is a measure of change, but God is perfect and unable to become better or worse. God is not within time, but time is within God. As for God’s omnipotence, we can see it in the depths of the ocean, the heights of the mountains – these are things that humans cannot make. In the orderliness of the universe, we can see God’s wisdom; and in the growth of creatures, we can see God’s goodness. Since God is wise and omnipotent, He has plans for His creatures and is able to carry them out – this is known as Providence. Irrational creatures are necessarily led by God, but rational creatures – i.e. angels and humans – may choose to either cooperate with or rebel against God. Even evil, the absence of good, is permitted by God in His wisdom so that all things might find their fulfillment in Him. All the saints have only done great deeds by trusting in God’s Providence.

In 1939, St. Josemaría Escrivá successfully escaped Communist territory and when the Spanish Civil War ended, he returned to Madrid. Opus Dei was criticized for being a secret society, so they received recognition from the Archbishop of Madrid in 1941 and from Pope Pius XII in 1950. Opus Dei had laity, married persons, and even some “co-operators”, some of whom were not even Catholics. These people helped Opus Dei in its ministries, like education and cultural works. Although persecution of Opus Dei continued, St. Josemaría responded not with enmity but prayer, and in 1951, he consecrated the families of all Opus Dei members to the Holy Family and the entire Opus Dei to the Immaculate Heart of Mary. He sent Opus Dei members around the world to spread the Gospel. He knew that the period of Vatican II would be a turbulent time, so he distributed Rosaries, asking for prayers for the Church, and went to Marian pilgrimage sites, praying for the Church himself. The saint passed away in 1975, hopeful of helping more people in Heaven, and was canonized by Pope John Paul II in 2002. He taught us that everyone has a vocation to holiness and has apostolic work.

In 1937, St. Josemaría Escrivá and his companions waited in the forest to be smuggled out of Communist territory. They made good use of their time in hiding – they would wake up at 7am, pray at 7:15am, celebrate Mass at 7:30am, pray the Rosary, and meditate. He assigned jobs to his companions: collecting wood, cleaning, keeping records, leading prayers, and giving talks on their occupations. One day, the time came to leave and St. Josemaría retrieved the Eucharist from a silver cigarette case for them to adore. On Sunday, they were climbing a mountain and decided to celebrate the Mass on the mountainside. The flat stone that served as the altar was so low that St. Josemaría had to kneel to celebrate Mass and needed his companions to shield the Eucharist from being blown away. They reached mountaintop before sunset thanks to St. Josemaría’s encouragement. But the next day, they had to climb another mountain, and his breathing became hurried. His companions had to carry him, but he said, “I have come not to be served, but to serve.” They began praying the Rosary, but with their hands occupied with climbing, they lost count. Some decades had 20-30 Hail Mary’s. Then, they reached the mountaintop.

In 1937, St. Josemaría Escrivá and his companions were smuggled out of Barcelona. Not long after, the Communist police cracked down on the place they had been staying at. During their escape, they stayed in a farmhouse and celebrated Mass with a glass as the chalice and a notebook as the Missal. There was still a risk of capture, so they moved to an abandoned rectory nearby. St. Josemaría began having doubts whether it was the will of God that he leave Madrid and escape Communist-controlled territory. He prayed to the Virgin Mary to give him a rose as a sign that he was doing the will of God. One day, as he told his companions that he would not be celebrating Mass, he went to an abandoned church and emerged ecstatic. In his hands was a wooden rose – he would celebrate Mass that day. At another time, they had to hide in a cabin in the woods to wait for more refugees before continuing. St. Josemaría named it St. Raphael’s Cabin and prayed for the angel’s intercession. As a witness later recounted, the Mass that he celebrated in the forest was very sacred. The priest was recollected and focused and the singing of birds added to the atmosphere.

St. Josemaría Escrivá had evaded capture thus far in Madrid during the Spanish Civil War, but his friends knew that it was a matter of time before he was caught by the Communists. They brought him to some smugglers in Barcelona, who would take him to the Nationalist-controlled area. St. Josemaría had an influential friend in Barcelona, an old classmate while studying law, and an atheist. Upon arrival in Barcelona, the friend invited him over for dinner and tried to convince him to accept a legal career to save his life. But St. Josemaría was adamant that he would not abandon his priestly vocation. Seeing this, the friend told him, “If you ever get captured, tell them you are my brother, and I will see what I can do.” In 1937, Barcelona suffered famine and in their apartment, a starving dog was so hungry that it ate the belt and sock of St. Josemaría’s travelling companion. Nonetheless, St. Josemaría gave his food to the poor children and when that ran out, he played with them, giving them love and concern.

During the Spanish Civil War, St. Josemaría Escrivá hid in the Honduran Consulate; not wanting to waste his time, he continued to celebrate the Mass, pray the Rosary, and meditate with fellow refugees. They also studied other languages in the hopes of spreading the Opus Dei around the world after the war. He personally wrote prolifically and read the classics and theological works. He also sought Confession from other priests once a week. A follower, named Isidoro, used his Argentine citizenship to transit freely in and out of Communist-occupied Madrid. He served as St. Josemaría’s messenger, carrying spiritual reflections and the Eucharist to others. However, as all priests in Madrid had either fled or were in hiding, many people died without receiving the Sacraments. St. Josemaría decided to leave the Consulate, carrying fake documents and dressed as a civilian. He prayed many Rosaries on the streets, heard Confessions, consoled people, and preached secretly. Sometimes, he would narrowly evade capture, saved only by the careful attention of his sympathizers.

For five months in the Spanish Civil War, St. Josemaría Escrivá hid from the Communists in an insane asylum. Many of the “patients” were actually refugees; as many of the medical staff had Communist sympathies, they would report suspected refugees to the secret police. However, some doctors taught St. Josemaría how to imitate an insane person. Assigned to him were three nurses – two of whom were Communist sympathizers and one, the head nurse María Luisa, who was a reliable person. St. Josemaría told her that he was a Catholic priest and asked her to stand guard as he celebrated Mass in his room. In 1936, due to the severe religious persecution, the Holy See exempted priests in Spain from the usual requirements of an altar, liturgical vessels, and vestments for celebrating the Mass. Every day, St. Josemaría secretly celebrated the Mass and brought the Eucharist to other political refugees in the asylum. He would also write letters to encourage the other patients, using codewords to disguise their contents: “Don Manuel” meant Jesus, “Don Manuel’s mother” meant Mary, and grandfather meant God the Father. St. Josemaría wrote his letters like a grandfather to his grandchildren. In 1937, he moved to hide at the Honduran Consulate; before leaving, he gave the Eucharist to the other refugees wrapped in paper so they could receive without touching it with their hands. Because consulates enjoy diplomatic immunity, they sheltered many Catholic refugees, although they suffered overcrowding and starvation. He would offer Mass every day on luggage cases as an altar, with a crystal glass as a chalice, and with a suit and tie as vestments.

During the Spanish Civil War, St. Josemaría Escrivá was on the run from the Communists. On August 28, 1936, he hid in the third-floor apartment of a man named Manuel and one of Manuel’s maternal relatives. The troops began searching from the ground floor up and the three men moved up to the rooftop and hid. As the troops neared, St. Josemaría told the relative, “I am a priest. If you wish, you can make a perfect contrition and your sins will be forgiven.” As the relative later recalled, revealing his priestly office was very courageous, for had the troops found them, he could have sold out St. Josemaría to save his own life. St. Josemaría began praying to his guardian angel, encouraged the other two men to do so too, and forgave their sins. They asked, “What will happen if they find and kill us?” He replied, “Then you will go to heaven.” The footsteps neared the door they were hiding behind, then stopped, and turned around. Of all the doors of the apartment, the soldiers neglected to search the one hiding the three men! At another time, St. Josemaría learned that his friend Fr. Pedro had been killed and he wept. Before the war, they had discussed the possibility of being martyred and had agreed that whichever one was martyred first would pray for the other in heaven. A few days before his death, Fr. Pedro said, “Now is the time to study the lives of the early Christians, to know how they worked amidst persecution, obeyed the Church, proclaimed Jesus Christ, prepared for martyrdom, forgave their persecutors. Fr. Pedro was canonized in 2003. Starting from October 1936, St. Josemaría hid in an insane asylum for five months.