Q: What is meant by ‘The Communion of Saints’ in the Apostles’ Creed?

A: By ‘The Communion of Saints’ is meant the union of the faithful on earth, the blessed in heaven, and the souls in purgatory, with Christ as their Head.

The blessed in heaven comprise the Church triumphant; the souls in purgatory, the Church suffering; and the faithful on earth, the Church militant.
"It is therefore a holy and wholesome thought to pray for the dead, that they may be loosed from sins" (2 Maccabees 12:46).
"In him (Christ Jesus) the whole structure is closely fitted together and grows into a temple holy in the Lord; in him you too are being built together into a dwelling place for God in the Spirit" (Ephesians 2:21-22).
"... Rendering thanks to the Father, who has made us worthy to share the lot of the saints in light" (Colossians 1:12).
"But you have come to Mount Sion, and to the city of the living God, the heavenly Jerusalem, and to the company of many thousands of angels, and to the Church of the firstborn who are enrolled in the heavens, and to God, the judge of all, and to the spirits of the just made perfect, and to Jesus, mediator of a new covenant" (Hebrews 12:22-24).

Q: Through the Communion of Saints, what can the blessed in heaven do for the souls in purgatory and the faithful on earth?

A: Through the Communion of Saints, the blessed in heaven can help the souls in purgatory and the faithful on earth by praying for them.

The prayers of the blessed in heaven are always efficacious because they are always in accord with God's will.
"When thou didst pray with tears, and didst bury the dead, and didst leave thy dinner, and hide the dead by day in thy house, and bury them by night, I offered thy prayer to the Lord" (Tobias 12:12).
"And there was given to him much incense, that he might offer it with the prayers of all the Saints upon the golden altar which is before the throne" (Apocalypse 8:3).

Q: Should the faithful on earth, through the communion of saints, honour the blessed in heaven and pray to them?

A: The faithful on earth, through the communion of saints, should honour the blessed in heaven and pray to them, because they are worthy of honor and as friends of God will help the faithful on earth.

Many Saints have special feast-days. All the Saints are honoured on the Feast of All Saints, November 1.
"Let us now praise men of renown, and our fathers in their generation" (Ecclesiasticus 44:1).

Q: Can the faithful on earth, through the Communion of Saints, relieve the sufferings of the souls in purgatory?

A: The faithful on earth, through the Communion of Saints, can relieve the sufferings of the souls in purgatory by prayer, fasting, and other good works, by indulgences, and by having Masses offered for them.

Mass can be frequently offered for the repose of a soul. There are special Requiem Masses for the day of the funeral, the thirtieth day after death or burial, and the anniversary of the death or burial. On All Souls' Day, November 2, Masses are offered for all the souls in purgatory.
Most indulgences granted by the Church are applicable to the poor souls in purgatory. A plenary indulgence can be gained by the celebration of Mass at a privileged altar. This indulgence can be applied only to the soul in purgatory for whom the Mass is offered.
Bishops and other prelates designated in the Code of Canon Law can determine and declare one altar, in churches specified by law, as privileged daily and perpetually, under the conditions prescribed by the Sacred Canons.
All Masses celebrated at any altar on All Souls' Day, and during its octave, and during the Forty Hours' Devotion enjoy the same privilege as those offered on a privileged altar, but only in favor of the soul for whom the Mass is said.
"It is therefore a holy and wholesome thought to pray for the dead, that they may be loosed from sins" (2 Maccabees 12:46).

Q: Can the faithful on earth help one another?

A: The faithful on earth, as members of the Mystical Body of Christ, can help one another by practicing supernatural charity and, especially, by performing the spiritual and corporal works of mercy.

Prayer, one of the spiritual works of mercy, is of value not only for the living but also for the dead. The other spiritual works of mercy and most of the corporal works are concerned primarily with the living.
"Then the king will say to those on his right hand, 'Come, blessed of my Father, take possession of the kingdom prepared for you from the foundation of the world; for I was hungry and you gave me to eat; I was thirsty and you gave me to drink; I was a stranger and you took me in; naked and you covered me; sick and you visited me; I was in prison and you came to me.' Then the just will answer him, saying, 'Lord, when did we see thee hungry, and feed thee; or thirsty, and give thee drink? And when did we see thee a stranger, and take thee in; or naked, and clothe thee? Or when did we see thee sick, or in prison, and come to thee?' And answering the king will say to them, 'Amen I say to you, as long as you did it for one of these, the least of my brethren, you did it for me' "(Matthew 25:34-40).
"By this will all men know that you are my disciples, if you have love for one another" (John 13:35).
"I urge therefore, first of all, that supplications, prayers, intercessions and thanksgivings be made for all men" (1 Timothy 2:1).
"Pray for one another that you may be saved. For the unceasing prayer of a just man is of great avail" (James 5:16).