I can never hear this beatitude, without simultaneously hearing St Paul 's injunction to the Philippians: " Rejoice in the Lord always. I repeat, rejoice " (Phil 4:4).

Note that Paul doesn't say rejoice in the Lord from time to time, or when the mood is upon you, but " always ." And yet, " Blessed are those who mourn."

Paradoxes of this kind mean that any contradiction we sense must be only apparent, not real. The way to resolve it is to strive for a deeper synthesis. Paul himself advised the community in Romans 12:15: " Weep with those who weep ." Not cheer up those who weep, but weep with them.

" Man was made for joy and woe ," wrote William Blake, " And when this we rightly know/Thro the world we safely go/Joy & Woe are woven fine/A Clothing for the Soul divine/Under very grief and pine/Runs a joy with silken twine ."

Suggested here are some lines of the synthesis I refer to, but we need to spend some time unpacking things. Joy and sorrow are inseparable in a sense deeper than being close companions in human experience.

They are essentially linked in that a real capacity for one is a real capacity for the other. Our hearts, in other words, cannot know the heights of joy unless they are familiar with depths of sorrow. If you run away from mourning, you are unlikely to know the meaning of rejoicing.

Joy is not mindless cheerfulness or a sentimental evasion of hard realities. Joy fully confronts such realities. Hence, in its deeper or sturdier manifestations, joy is always marked by a certain gravity. Alleluia , Thomas Merton once reminded us, is a song of the desert.

But the beatitude does not consider mourning " blessed " because of its essential connection with joy. The benediction has to do with mourning itself as a disposition.

To mourn is not simply to grieve, though grief for the many forms of loss we suffer is not excluded. The meaning can be grasped from the promised relief. Blessed are they that mourn, for they shall be comforted .

The "comfort" promised is not the kind word or embrace that often brings an end to human discomfort. "Comfort" is a major Biblical synonym for "salvation," and that is what the beatitude has in mind. Isaiah chapter 40 is an intense hymn, a paean, to salvation as "comfort." " Comfort my people, comfort them, says your God. Speak to the heart of Jerusalem.Go up on a high mountain.Shout fearlessly, say to the towns of Judah, 'Here is your God '" (Is 40:1, 9).

The message shouted is that Yahweh comes to save. This is why, according Aquinas and many of the Fathers of the Church, the mourning the beatitude pronounces blessed is linked with the gift of knowledge.

To know the truth of the human predicament, that is, to know it without salvation, is to know it as something that can only be met with mourning.

The Roman poet Lucretius expressed it well centuries ago. The first thing an infant does, he wrote, when it comes into the world is cry. And with good reason, he adds, considering where it suddenly finds itself.

Behind such sentiments is not so much cynicism as the "mourning" of our Beatitude. It is the longing for a different world, a different human prospect. Lucretius was not alone in this. The most sensitive minds of the pre-Christian era were always sad.

Mourning is the effect of seeing things as they are, and ourselves as we are, without illusion. It is not grieving without a reason. It is the honest awareness of our part in the breakdown of a fallen world, where even the strongest among us are incapable of finally helping ourselves, where all of us are heading for death.

In this way mourning is also an entrée into the passion of Christ. Why did Christ have to suffer? Because suffering is where human beings were and are. If he wished to save them, there is where he had to go. That's the "necessity" of the Cross.

The true face of our plight is thus always the face of Christ, who, as St Gregory of Nazianzus put it, "bears all me and all mine in himself."

Theologically and spiritually, this changes everything. Empirically, it changes nothing. The actual quality of our suffering doesn't change. Our union with Christ, or rather His union with us, gives us a particular perspective, and a particular capacity to bear with ourselves, one another, and with the world itself.

In this bearing, the passion of mourning becomes compassion, a form of suffering with. It is our own suffering we bear, but suffering recognised as taken up by Christ, and therefore suffering united with everybody else's. It is here that mourning opens out into charity, that is, it refuses the useless luxury of self-pity and turns outwards in the fellowship of the redeemed.

Here, too, mourning becomes one with joy, because joy finally is the conviction that Christ is God's "Yes" upon the world and all life in it. Paul also wrote of that conviction, and you can hear joy's passionate lyricism in his words: " For I am certain of this: neither death nor life, nor angels, nor principalities, nothing already in existence and nothing still to come, nor any power, nor the heights nor the depths, nor any created thing whatever, will be able to come between us and the love of God, revealed in Jesus Christ ."