This is an extract from a paper by the Rev Dr Robert Crouse.
All human desire, all human longing and aspiration, expressed in a thousand different forms, at a thousand different levels, is ultimately desire for God. Dante makes that point lucidly in the Convivio: Therefore, I say that not only in the gaining of knowledge and wealth, but in any acquisition whatever, human desire reaches out, in one way or another. And the reason is this: the deepest desire of each thing, arising from its very nature, is to return to its principle. And because God is the principle of our soul, and has made it like himself (as it is written, “Let us make man in our image and likeness“), the soul mightily desires to return to him.
The articulation of desire, the articulation of human longings and aspirations: from the standpoint of human psychology and universal religious practice, that is the meaning of prayer. It is homesickness for God. “My soul thirsts for you, my flesh longs after you: in a barren and dry land where no water is.” (Ps. 63:2). But looked at only in that perspective—the perspective of human aspiration and human experience—it has inevitably a tragic character, because it seeks an end which human energy and human ingenuity can never attain: it seeks the divine life, it seeks divine friendship, it seeks to be as God. That is tragic hubris, the tragic pride of human aspiration, whether one thinks of that in terms of the biblical accounts of the expulsion from the garden, and the destruction of the Tower of Babel, or whether one thinks of the fate of the heroes of Greek tragic poetry; for the divine life and the divine friendship appear to be, as Aristotle remarks, “a life too high for man.” 
But what is the alternative? To deny the desire is to reduce the quest for truth to idle curiosity or pedestrian utility, the quest for happiness to selfish self-indulgence, and the quest for beauty to the search for emotional “highs”.
To such an account of human prayer as human desire, Christian theology would add another, and more profound, and for Christian prayer altogether crucial perspective, in the recognition of prayer as divine gift in creation and redemption, inspired by the divine Word and moved by the divine Spirit. St. Augustine makes the point in a famous passage at the beginning of the Confessions. “It is you, O God, who rouse mankind to delight in praising you, for you have made us for yourself, and our hearts are restless, until they find their rest in you.”  In another passage, near the end of the Confessions, he comments more fully on the meaning of that unquiet heart:
By its own weight, a body inclines towards it own place. Weight does not always tend towards the lowest place, but towards its own place. A stone falls, but fire rises. They move according to their own weights, they seek their own places. Oil poured into water rises to the surface; water poured on oil sinks below the oil. They act according to their own weights, they seek their own places. Things out of place are restless. They find their own places, and then they rest.
My love is my weight (pondus meum amor meus). Whithersoever I am moved, I am moved there by love. By your gift (dono tuo = the Holy Spirit), O Lord, we are set on fire, and are borne aloft: we burn, and we are on the way. We climb the ascents that are in the heart….With your fire, with your good fire, we burn and go on, for we go up to the peace of Jerusalem. 
The activity of prayer is thus the activity of love’s conversion, the activity of rational will aspiring and ascending towards its true, eternal good. But what is the impulse, the spring of this ascent, this pondus, this “weight” of love? It is the natural God-given desire of the created soul, “the concreated and everlasting thirst for God’s own realm,”  inspired by the fire of the spirit, which burns within the soul. And just as fire, by the compulsion of its very nature, rises upwards, so the soul moves to desire, and finds no rest until it finds rejoicing in the final object of its love.
But whereas in the realm of nature all things are created in number, measure and weight, and by their very natures, by their rising and decline, infallibly seek the good in ordered and harmonious praise of the Creator, human love is the activity of free and rational will; and therein lies the possibility of wayward love: a love which fixes upon some finite good as though that were the absolute and perfect good. Thus, in human life, love becomes distorted, perverted, and frustrated, and leads the soul to slavery – subservience to the sensible, to idle curiosity and vain ambition, subject to all the demons of the present age. And thus, the true freedom of the will is lost; the fire of love is, as it were, extinguished, frozen in a dark abyss of alienation and despair, and prayer is dead. But still, somehow, the thirst is there, if only in a half-recognised sense of emptiness and futility: “Like as the hart desires the water brook, even so my soul longs after you, O God.”
That text from Psalm 42 is marvellously illustrated in the great twelfth-century mosaic (just now beautifully restored) which adorns the apse of the ancient Church of San Clemente, in Rome. In that picture, the harts come to drink of the streams of paradise which flow from the Garden of Eden, which is also the hill of Calvary, surmounted by the Tree of Life, which is also the Cross of Christ. There is much more symbolic richness in that astonishing mosaic,  but the essential point for us now is just this: It is through the Cross of Christ that the ancient enmity, the old and ever new alienation, is overcome, and the streams of grace flow out to renew the spiritual life of humankind, and give rebirth to prayer.
It is through the Cross of Christ that the gates of prayer are truly opened. Prayer is, indeed, the articulation of human desire; but Christian theology sees it as properly much more than that. By the Cross, we are raised up, no longer just clients, so to speak, but friends of God; and prayer becomes the conversation, the communication of friends. As St Thomas Aquinas remarks, in his meditations of St. John 15 (Jesus’ Last Supper Discourse), Our Saviour calls his disciples “friends,” and to converse together in the proper condition of friendship. Friends delight in each other’s presence, and find comfort there in their anxieties. We are made friends with God, he dwelling in us, and we in him. We are no longer servants, but friends, “For ye have not received the spirit of bondage again to fear, but ye have received the Spirit of adoption, whereby we cry, Abba, Father” (Rom. 8, 15). 
The great Puritan divine, Richard Baxter, makes just the same point as St Thomas, specifically with reference to the Lord’s Supper, wherein, he says, “we have the fullest intimation, expression and communication of the wondrous love of God.”
In the sacrament of the body and blood of Christ, we are called to a familiar converse with God…. There we are entertained by God as friends…and that at the most costly feast. If ever a believer may on earth expect his kindest entertainment, and near access, and a humble intimacy with his Lord, it is in the participation of this sacrifice feast, which is called the Communion. 
It is, of course, a token of the intimacy of divine and human friendship that in the language of prayer, in English as in many other languages, we are privileged to use the intimate, second person singular forms, the “thee” and “thou” and “thine” of intimate friends, rather than the public and formal plurals. Prayer is the conversation of intimate friends. But the theology of Christian prayer takes us even beyond the intimacy of friendship: “Your life is hidden with Christ in God” (Col. 3:3): “I live, yet not I, but Christ lives in me” (Gal. 2:20). We dwell not only in God’s presence, as friends, but we dwell in him and he in us, and rightly does George Herbert speak of prayer as “God’s breath in man returning to his birth.” 
Indeed, in prayer we are taken up into the deepest mystery of the divine life, in the relations of being, knowing and loving which are the Holy Trinity. Through the gift of the Spirit, the Word of God engraces our hearts to cry, “Abba, Father,” and thus we have our places in that eternal outgoing and return of the divine Word and Spirit, the divine self-knowing, and the bond of love which unites the knowing and the known.
Thus our prayer approaches God not from outside, as it were, but from within, “through Jesus Christ our Lord, in the power of the Holy Spirit“; that is to say, our prayer is within the knowing and willing of God, within the divine Providence. In a right understanding of prayer, it can stand in no ultimate opposition to divine Providence, because its whole point, really, is to place our life freely within God’s will, in knowledge and love; and our prayers accomplish precisely what God’s eternal Providence, the source of all order in the world, has eternally willed to accomplish by them. They are the free agents of Providence, the free, rational and willing instruments of grace. God’s grace descends, and ascends again in prayer. As Richard Hooker beautifully expresses it:
For what is the assembling of the Church to learn, but the receiving of Angels descended from above? What to pray, but the ascending of Angels upward? His heavenly inspirations and our holy desires are so many Angels of intercourse and commerce between God and us. 
God’s grace descends, and ascends again in prayer. Thus prayer is God’s gift to us: God’s work in us and our life in God, the redemption of desire. As St. Paul explains, all who are in Christ are, by God’s grace, new creations (2 Cor. 5:17), and our prayer is our participation in that new life of grace, converting us, setting straight our love, transforming, transfiguring, “transhumanizing” us (to borrow Dante’s special word, transumanar). 
And at this level, when we speak of prayer, we’re not speaking just of particular acts of prayer, or occasional prayer, but of prayer as a condition of life in continual conversion, continual reference to God. That is habitual prayer, that state in which, according to the magnificent Prayer Book collect for the Fourth Sunday after Easter, God so orders our unruly wills and affections that we love what he commands and desire what he promises, that so our hearts may surely there be fixed where true joys are to be found. In that condition of habitual prayer, that state of being in prayer, as John Donne says, in one of his sermons, “that soul prays sometimes when it does not know that it prays.” 
In Christ, we are new creations, born anew, no longer at enmity, but friends of God. Our reconciliation has been accomplished, once for all; for Christ’s sake, we are accounted friends of God. But in another sense, our reconciliation is not complete, and will not be complete, until we come to know as we are known and to love as we are loved. Thus, there is the tension between a justification, divinely-wrought and finished once for all, and a sanctification, which is being worked out within us day by day. Prayer reaches out, in faith and hope, across that space.
In that reaching out of prayer, precisely because it is by faith, trials and temptations, the dark night of doubt, confusion and uncertainty, are not just unfortunate accidents. In God’s good Providence, they belong to the very life of faith, for faith must be tried, like precious metal, “which from the earth is tried, and purified seven times in the fire” (Ps. 12:6; I Peter, 1:7). As St. Ignatius of Antioch puts it, our desire is crucified: “My love,” he says, “my eros is crucified.”  Perhaps the trials take different forms in one age or another, and different forms for each of us. Those trials are necessary, and must be embraced. Indeed, as St. James says, we must “count it all joy, knowing that the trial of your faith worketh patience. Let patience have her perfect work, that ye may be perfect and entire.” (Jas. 1: 3-4).
In this mixed time, which is both glorious and hard, we are not without resources. We do possess, in faith, God’s word of reconciliation, committed unto us. We do possess, in faith, God’s work for us, God’s word to us, made audible in Holy Scriptures, made sensible in Holy Sacraments, if we will but attend with minds and hearts obedient and penitent. We do possess, in faith, the gift of God’s Spirit to lead us into truth. We do possess, if we will, in the community of faith, centuries of wisdom and experience—none of it irrelevant—words and images of prayer and sanctity which will come alive for us, if we will give them (as to the shades in Homer’s Hades) the living blood of our own labours to drink. It seems to me terribly important and urgent that we do our best to reclaim that great heritage of prayer and spiritual discipline which is ours especially as Anglicans in our great tradition of common prayer. What is essentially required is the practical upbuilding, among us and within us, of the life of penitential adoration, the life of habitual prayer. With such graces, may God now refurbish his house.
Why are you so full of heaviness, O my soul?
and why are you so disquieted within me?
O put your trust in God, for I will yet give him thanks,
who is the help of my countenance, and my God.
- Aristotle, Nichomachaen Ethics, X, 7 (1177b 25); cf. Metaphysics, XII, 7 (1072b 15-20). On the impossibility of friendship with God, Nic. Ethics, VIII, 7 (1158b 35-1159a 5).
- Augustine, Confessions, I, 1.
- Ibid. XIII, 9 (tr. R.D.C.). For a full discussion, see A. DiGiovanni, L’inquietudine dell’ anima. La dottrina dell’ amore nelle “Confessioni” di S. Agostino (Rome, 1964).
- Dante, Divine Comedy. Paradiso, ed. cit.,II, 19-20, p. 622.
- For a detailed description, see L. Boyle, A Short Guide to St. Clements’, Rome (Rome, 1972), pp. 26-32.
- Thomas Aquinas, Contra Gentiles, IV, 22; cf. Super Evan. S. Jo. lect., XV, ed. Marietti, lect. 3, 1-4, pp. 379-382.
- Richard Baxter, Works, III, 816, as quoted in J. Packer, A Quest for Godliness (Wheaton, Ill., 1980), pp. 213-214.
- George Herbert, Prayer, ed. cit., p. 139.
- Richard Hooker, Of the Laws of Ecclesiastical Polity, ed. cit., V, xxiii, p. 115.
- Dante, Divine Comedy, Paradiso, ed. cit., I, 70, p. 619.
- John Donne, Sermon 12, in G. Potter and E. Simpson, eds., The Sermons of John Donne (Berkeley and Los Angeles, 1962) Vol. IV, p. 310.
- Ignatius of Antioch, Ep. to the Romans, VII, (ed. K. Bihlmeyer, Die Apostolischen Väter (Tübingen, 1956) I, 16, p. 100.