1. The lowest grade is that of petitionary prayer for material benefits. One asks for mundane benefits whether for oneself, or, as in the case of intercessory prayer, for another. In its crassest forms it borders on idolatry and superstition. A skier who prays for snow, for example, makes of God a supplier of mundane benefits, and this borders on idolatry, the worshipping of a false god, a sort of cosmic Candy Man, an anthropomorphic projection.
As for superstition, consider the case of a believer who places a plastic Jesus icon on the dashboard of her car. Anyone who believes that a piece of plastic has the power to ward off automotive danger is superstitious. A hunk of mere matter cannot have such magical properties. Superstition in this first sense seems to involve a failure to understand the causal structure of the world or the laws of probability. A flight attendant who attributes her years of flying without mishap to her wearing of a rabbit's foot or St. Christopher's medal is clearly superstitious in this first sense. Such objects have no causal bearing on an airplane's safety.
But no sophisticated believer attributes powers to the icon itself. The sophisticated believer distinguishes between the icon and the spiritual reality or person it represents.
Well, what about the belief that the person represented will ward off danger and protect the believer from physical mishap? That belief too is arguably, though not obviously, superstitious. Why should the Second Person of the Trinity care about one's automotive adventures? Does one really expect, let alone deserve, divine intervention for the sake of one's petty concerns?
But what if the icon serves to remind the believer of her faith commitment rather than to propitiate or influence a godlike person for egoistic ends? Here we approach a form of religious belief that is not superstitious. The believer is not attributing magical powers to a hunk of plastic or a piece of metal. Nor is she invoking a spiritual reality in an attempt to satisfy petty material needs. Her belief transcends the sphere of egoic concerns, and respects the divine transcendence.
2. The next grade up is petitionary prayer for spiritual benefits. At this level one is not asking for one's daily material bread, panem quotidianum, but for such spiritual or ‘supersubstantial’ bread, panem supersubstantialem, as acceptance, equanimity, patience, courage, and the like in the face of the fact that one lacks material bread or has cancer. "Thy Will be done." One asks for forgiveness and for the ability to forgive others. One prays for a lively sense of one's own manifold shortcomings, for self-knowledge and freedom from self-deception. One prays, not to be cured of the cancer, but to bear it with courage. One prays for the ability to see one's tribulations under the aspect of eternity or with the sort of detachment with which one contemplates the sufferings of others.
3. Higher still is prayer that is wholly non-petitionary. At this level one asks neither for material nor for spiritual benefits. One form of this is prayer is sheer gratitude for what one has. Prayer as thanksgiving. Prayer as praise. Beyond this there is prayer as pure aspiration, as a straining of the soul upwards. A pure spiritual seeking, ascending, soaring. One seeks to elevate oneself above one's perceived infirmity and wretchedness. One seeks to rise above the paltriness, crudity, baseness of one's usual thoughts and emotions. Not a petitioning, but a self-elevating and a leaving of oneself behind.
4. Prayer as aspiration may then lead on to forms of non-discursive meditation proper and infused contemplation. At the first stage of non-discursive meditation the soul enters mental silence and rests there having abandoned all petitioning and aspiring. One is no longer working but resting in mental silence. The great Spanish mystic Teresa of Avila calls this the Prayer of Quiet and classifies it as the lowest level of infused contemplation in the Fourth Mansion of her Interior Castle. Within this silence one receives mystical grace which comes from without the mind, grace that cannot be acquired by one’s own efforts. Beyond this there are higher levels of infused contemplation such as the Prayer of Union.
5. I don't know quite what to do with Weilian prayer. The ascending ladder of prayer is a ladder of purification. See Simone Weil, Gravity and Grace, Routledge 1995, p. 19: "A method of purification: to pray to God, not only in secret as far as men are concerned, but with the thought that God does not exist." Is this the purest form of prayer, prayer bereft of every petition, bereft even of the hope of attaining anything at all, or is this form of prayer but an expression of Weil's extremism? And perhaps nihilism?
God cannot be a being among beings. This is ruled out by the divine transcendence. But is God so utterly transcendent that he is beyond the Aquinate characterization of God as self-subsisting Being, ipsum esse subsistens? For Aquinas, God is Being (esse) itself, not a being, ens. God does not participate in Being analogously as the present participle ens participates in the infinitive esse; God is (identical to) Being. But he is, as self-subsisting, not nothing either, and so he is. In Aquinas God is the mystical unity of esse (to be) with id quo est (that which is). God is the mystical unity of He Who Is with Being itself. This of course makes no sense to the discursive intellect, which thinks in opposites and keeps opposites in opposition, lest it cease to be what it is. But we reached this outer Aquinate limit by a discursive route, not be mystical intuition. The question is whether we should take it one step further, and think of God as not only beyond every being (ens) but also beyond Being (esse). Is the febrile Weil pointing us in the direction of the identity of Being and Nonbeing? Is God aufgehoben ('simultaneously’ but eternally cancelled and preserved) in this identity?