Why do Catholics celebrate the feast of All Saints?

Saints of God: Come to our aid!

One of our greatest abbots and Doctors of the Church, St Bernard of Clairvaux, answered this question in an eloquent homily, parts of which I have reproduced below: -

Of what profit to the saints are our prayers and the honour we pay them? Of what use is this feast-day? Of what use to them are honours paid on earth when our heavenly Father, fulfilling the faithful promise of his Son, has raised them to glory? What does our commendation mean to them? The saints have no need of honour from us; neither does our devotion add the slightest thing to what is theirs. Surely we are the ones to benefit, when we venerate their memory. I confess that at the very thought of them I feel myself inflamed by a tremendous yearning to be with them. 

Calling the saints to mind inspires, or rather arouses in us, above all else, a longing to enjoy their company, so desirable in itself. We long to share in the citizenship of heaven, to dwell with the spirits of the blessed, to join the assembly of patriarchs, the ranks of the prophets, the council of apostles, the great host of martyrs, the noble college of confessors and the choirs of virgins. In short, we long to be united in the communion of all the saints. The Church of all the first followers of Christ in glory awaits us, but we turn aside; the saints lovingly call us, and we make little of it; the host of the redeemed look for us, and we are not interested. 

Brothers, at long last let us shake off our torpor and rise with Christ to seek the things that are above, to set our mind on the things of heaven. Let us long for those who are longing for us, hasten to those who are waiting for us, and with our prayers come into the presence of those who are looking for us. We should not only want to be with the saints, we should also hope to possess their joy. While we desire to be in their company, we must also earnestly seek to share in their glory. Do not imagine that there is anything harmful in such an ambition as this; there is no peril in setting our hearts on such glory. 

When we commemorate the saints we are inflamed with another yearning: that Christ our life may also be made manifest to us as he appeared to them and that we may one day share in his glory. Until then we see him, not as he is, but as he became for our sake. He is our head, crowned, not with glory, but with the thorns of our sins. As members of that head, crowned with thorns, we should be ashamed to live in luxury when the purple robes are put on him in mockery rather than honour. When Christ comes again, his death shall no longer be proclaimed, and we shall know that we also have died, and that our life is hidden with him. The glorious head of the Church will appear and his glorified members will shine in splendour with him, when he forms this lowly body anew into such glory as belongs to himself, its head. 

So, let us strive to attain this glory with a passionate desire and an ambition that is entirely praiseworthy. That we may rightly hope and strive for such blessedness, we must above all seek the prayers of the saints. Thus, what is beyond our own unaided efforts may be granted to us through their intercession. 

                               St Bernard of Clairvaux, Sermon 2 (emphases mine) 

Today is the Solemnity of All Saints, one of the Church's holiest and most ancient of feasts. This festival has been celebrated on 1 November in the Latin Church since the mid-8th century - although had previously been kept on 13 May since AD 609. Eastern Christians have celebrated this feast since the 5th century, and continue to do so on the Sunday after Pentecost (which is called All Saints' Sunday).

In reality, today's feast is a celebration of the fullness of Christ's glory made manifest in the members of his Body, the Church. Those men and women who conformed themselves to Christ in this life are now one with him in Heaven - they are where we long to be, they have achieved our own life's ambition. The Saints are completely one with Christ, living in the heart of the Trinity. They are the first-fruits of Our Lord's Holy Resurrection.

All Saints is therefore a day when we rejoice in the true and eternal vocation of every human being - one which Christians have been especially called to achieve through God's grace. It is also a day when we should ensure that we do not turn aside from Christ's first followers, or ignore those souls who are already waiting us in the blissful joy that is our heavenly and everlasting home! It is a day, then, for us to rededicate ourselves in our ambition for the things of Heaven.

Omnes sancti Angeli et Archángeli, oráte pro nobis!

Posted by Dylan Parry (A Reluctant Sinner)