It’s always easier to speak from experience, in which case the best reply to this question would come from Doctors of the Church Hildegard of Bingen (recently named) and Catherine of Siena as well as other saints like Francis of Assisi, Bernadette of Lourdes, or any number of folks on the biblical record like Jacob, Isaiah, Ezekiel, Peter, Paul, and John of Patmos, who wrote the Book of Revelation.

ICON of Hildegard of Bingen

From me, you can get a definition. Visions are understood to be the product of God’s self-communication. As Carmelite Father John Welch puts it, all of Christianity depends on divine revelation, so the hop to visions is not all that unusual for people of faith. Nonetheless it is an extraordinary event that can be expressed in words, ideas, or images. It may have a physical dimension but is more often experienced in the imagination or intuitive understanding.

Visions that include a tangible dimension are considered extremely rare. Juan Diego got an image on tilma cloak from Our Lady of Guadalupe. Philip Neri experienced a globe of fire entering his chest that literally broke his ribs and enlarged his heart. Francis of Assisi had his stigmata. Most visions don’t have that kind of corporeal aspect, and mystics themselves often mistrusted them if they did. “Imaginative visions”—Joan of Arc described hers this way—are often attributed to factors like youth, an elementary religious education, or psychological simplicity. Consider how many mystics had their experiences as children, like those of the Virgin Mary at Fatima, Portugal in 1917.

Mystics agree the most reliable visions are intellectual or intuitive; these are less likely to be distorted by unreliable human senses. Mystics are also the first to say that visions are not the goal of the spiritual life. Most mystics had their visions early and moved into a greater interiority of spiritual communion with God after that. In that sense the vision achieved its purpose along the spiritual journey as a boost upward into something richer and more useful—the point being, for the saints and for the rest of us, that we shouldn’t measure ourselves against these experiences or hanker after them. If even visionaries found them dispensable, they are clearly not prerequisites to grace.

Although faith is based on revelation, church teaching leaves the matter of specific visions open to question. Visionaries in modern times are subject to investigation by church authorities and may be deemed credible—but their experiences are not made matters for doctrinal acceptance for believers. Most of us have inexplicable episodes when we perceive things we have no way of knowing and yet do. If we pay attention, we might see more than we think.

Scripture
• Genesis 32:23-33; Isaiah 6:1-8; Ezekiel 10; Daniel 7:13-18; Acts of the Apostles 9:1-9; 10:9-16; the Book of Revelation

Online
• The Dialogue of Saint Catherine of Siena, "dictated by her, while in a state of ecstasy, to her secretaries, and completed in the year of our lord 1370"

Books
• Our Lady of the Lost and Found: A Novel of Mary, Faith, and Friendship by Diane Schoemperlen (Penguin, 2002)
• Mystics and Miracles: True Stories of Lives Touched by God by Bert Ghezzi (Loyola Press, 2002)

This phrase appears in the less commonly prayed Apostles’ Creed (not in the Nicene Creed usually recited at Mass), which may account for why more pew-sitters don’t question them. After all, church teaching defines hell as the place of the damned. Why would Jesus visit those who cannot be saved?

ICON of Jesus descending into hell (detail).

The answer lies buried in scripture, as it often does. Theologically, hell derives from an earlier conception of Sheol (Hebrew) and Hades (Greek). Whatever you call it, ancient ideas about the afterlife weren’t pretty. There was no life after death in the ancient reckoning: just an underworld of disembodied bare consciousness without volition or motion. Forget everything you know about Judgment Day: the good, the bad, and the boring were all presumed to end up in the same spiritual substrata of uselessness. The dead were called shades, literally shadows of their former selves. Unable to will or to act, they simply moldered together and lamented their lost opportunities.

In the great epic writings of the ancients, heroes often visited the underworld looking for answers, vanquished enemies, or old friends. They might talk to them but they couldn’t offer any assistance. The story of Jesus is different. A wonderful homily for Holy Saturday found in the Liturgy of the Hours’ Office of Readings says it all: “Today a great silence reigns on earth, a great silence and a great stillness . . . because the King is asleep. . . . He has gone to search for Adam, our first father, as for a lost sheep. Greatly desiring to visit those who live in darkness and in the shadow of death, he has gone to free from sorrow Adam in his bonds and Eve, captive with him . . . ‘I did not create you to be a prisoner in hell. Rise from the dead, for I am the life of the dead’ ” (see the Catechism of the Catholic Church, no. 635).

The idea that Jesus went to the dead first with the good news of the Resurrection is not a fabrication of early homilists. John’s gospel claims: “The hour is coming and is here now when the dead will hear the voice of the Son of God, and those who hear will live” (5:25). Luke picks up the theme in Acts, and Paul alludes to it in his letters. The First Letter of Peter says that after being put to death Christ “went to preach to the spirits in prison, who had once been disobedient” and that “the gospel was preached even to the dead” (3:18-19; 4:6). So that answers the question: Jesus went to the dead first to bring good news to those who needed it the most.

Scripture
• Psalms 6:6; 88:2-13; Matthew 12:40; John 5:25; Acts 2:24-31; Romans 8:11; 10:7; 1 Corinthians 15:20; Philippians 2:10; Ephesians 4:9; Hebrews 2:14-15; 13:20; 1 Peter 3:18-19; 4:6; Revelation 1:18

Books
• Death and Afterlife: A Theological Introduction by Terrence Nichols (Brazos Press, 2010)
• Shades of Sheol: Death and Afterlife in the Old Testament by Philip S. Johnston (IVP Academic, 2002)

Angels come first in the discussion, because they literally came first. God made only one kind of purely spiritual being. Unlike mortals, created at a belated stage of the story, angels are incorporeal, immortal creatures. But like us they received the gift of free will and could choose once: to serve or not serve God.

Traditions from outside scripture (but hinted at in many biblical passages) tell us how the decision unfolded. Most angels chose to serve. One, however, refused and drew others to join the revolt against God: by definition, the revolt against goodness. Hell came into existence as the end result of choosing to absent oneself from God's presence and good purpose.

So Satan and his demons are in fact angels, though we know them better as "devils." Their existence is geared to associate human beings with revolt against God. Meanwhile the heavenly host is dedicated to God's service in a variety of ways. Some serve celestially in the divine liturgy, offering endless praise and glory to God. Others serve as messengers, guardians, and protectors for the sake of humanity. In Judaism, Christianity, and Islam the teachings and traditions about angels are fairly consistent and complementary.

When Jesus proclaims the coming of the kingdom of God, he accompanies and ratifies this proclamation by casting out demons. Demons know who Jesus is, and they flee from his presence. That reminds us we have no reason to fear the demonic if we associate ourselves with God's presence and purpose revealed in Jesus.

Two things to keep in mind regarding angels and demons: 1. We are freer than they are because we can freely choose to serve or not serve God continually throughout our lives. 2. Because we are free, we can never blame "the devil" for anything we do. What we make of each decision is up to us.

Scripture
Book of Tobit; Job 1:1-2:10; Isaiah 6:1-8; Daniel 3; Matthew 1:18-2:23; Luke 1:5-38; Hebrews 1:1-2:18; Book of Revelation

Online resource
"Angels" by Father Paul Turner

Books
A Catalogue of Angels: The Heavenly, the Fallen, and the Holy Ones Among Us by Vinita Hampton Wright (Paraclete Press, 2006)
The Angels and Their Mission: According to the Fathers of the Church by Jean Danielou, S.J. (Sophia Institute Press, 2009)

This is the post-Halloween question I was waiting for! It’s a good question, especially for those old enough to remember when the Trinity was defined as “Father, Son, and Holy Ghost.” First, the word ghost comes from the German Geist, which means “spirit.” So there is less difference between these terms than we normally ascribe. Our modern idea of ghosts, however, is so shaped by horror films and the occult that I can’t say simply: Yes, Catholicism admits the reality of ghosts. Let me take a longer route to the answer.

Catholicism teaches that we are both body and soul, or as Saint Paul says (using the Greek for these words), flesh and spirit. The soul is a “substantial and spiritual principle endowed with immortality” according to the Catholic Encyclopedia. It’s substantial because it has elements of being, such as potency, stability, and the capacity to be modified. It’s spiritual in that it is immaterial and has intelligence and free will—irrespective of its relationship to a physical body. When we die, the soul separates from the body, to be reunited “at the end of the ages.”

Jesuit John Hardon in his Modern Catholic Dictionary notes that God may and does permit the souls of the dead to appear before the living when it’s suitable for our salvation. The lives of the saints are full of such apparitions. Church teaching, based in biblical tradition, warns against trying to conjure or control such spirits as occult practices routinely do. That means just say no to Ouija boards, séances, mediums, automatic writing, tarot cards, or other supernatural methods for obtaining information.

Seeking the aid of powers other than God is a deterrent to faith, does not lead to good, and can lead to harm. That is the Catholic position on the supernatural in general. Note: It is not a refutation of the existence of supernatural things, angels, demons, and “ghosts” included. In fact, because exorcism is still on the books in Catholic teaching, it would confirm rather than deny the reality of the spiritual world.

But for heaven’s sake, none of this should make you scared! Catholics believe that God alone is sovereign, and there is no power or principality equal to divine authority—Satan included. Lost souls aren’t wandering around aimlessly or even purposefully to get you. All created things must answer to God, just like you and me. The Ghost you’re most likely to engage is a Holy one.

Scripture
• Deuteronomy 18:9-14; 1 Samuel 28:4-25; 2 Kings 21:6; Isaiah 3:1-3; Micah 5:11; Acts 7:51-53; 13:6-12; 16:16-24; 19:13-20

Online
• "I believe in life everlasting," Catechism of the Catholic Church

Books
• Our Lady of the Lost and Found: A Novel of Mary, Faith, and Friendship by Diane Schoemperlen (Penguin Books, 2001)
• Apparitions of Modern Saints by Patricia Treece (Charis Books, 2001)

Discernment of spirits is as old as the church and as fresh as you and me, because anyone on the God-quest needs to know how to detect the divine fingerprint along the way. The question came up a lot in the early church: Saint Paul addresses it in letters to four different communities!

From Genesis forward the Bible contains stories of people confronting both good and evil spirits in many forms. Adam and Eve knew God and still bet wrong on the serpent. Abraham gambled more effectively when three strangers showed up at his tent. Jacob was never a God-centered chap and so had no clue what he was wrestling with that night he had his grip on an angel. Learning to tell good from evil isn’t enough, of course: King David knew better but chose poorly the night he laid eyes on Bathsheba.

Paul loves to talk about divine mysteries, but the discernment of spirits isn’t in that category for him. Discernment is a gift of the Holy Spirit, clearly identified by the fruits it produces, just as Jesus once said: “Each tree is known by its own fruit.” Paul spells out which fruits come from which baskets in Galatians 5. If you’re pursuing the idea of religious life, say, and the experience fills you with “love, joy, peace, patience, kindness, generosity, faithfulness, gentleness, and self-control,” Paul would call that a validated discernment. If on the other hand you wind up with a rotten bunch of fruit—immorality, idolatry, rivalry, jealousy, acts of selfishness, factions” and so on (it’s quite a list in Galatians 5!)—chances are the proposal is in error.

Paul’s also clear in 1 Corinthians 12 that discernment of spirits is a gift some enjoy as a specialty. It’s the “many parts, one body” idea: Not all are great at everything, which is why we must be church together. If you’re the Jacob-type wrestling with anonymous spirits in the dark, by all means seek spiritual direction from someone better at discerning spirits. Blessings on the journey!

Scripture
• Genesis 32:23-31; Romans 12:2-8; 1 Corinthians 12:4-11; Galatians 5:16-26; 1 Thessalonians 5:19-22

Online
• Vocation Match: Fill out a short profile to find which of the more than 250 religious communities are compatible with you
• Biblical Catechesis on Vocations: Message of Pope John Paul II for the World Day of Prayer for Vocations (April 20, 1997)

Books
• The Discerning Heart: Exploring the Christian Path by Wilkie W. Au and Noreen Cannon Au (Paulist Press, 2006)
• Discernment: A Path to Spiritual Awakening by Rose Mary Dougherty (Paulist Press, 2009)