...we can say that for Thomas a person succeeds in living the happy life when she gets to do, regularly and routinely, what she “really wants.”
But here the force of the word “really” is not, as before, that in which it contrasts with the false perceptions of desire that characterize the self-deceived . There is a very profound sense in which even the most perfectly honest person may not know what she wants: not, that is, the case where, of two things both of which she wants, she does not know which to choose, like whether to marry John or James. More problematic is the case where there is something that we want but we do not know what it is, except that it is somehow importantly connected with our happiness. Such is the case when we are morally befogged, because our deepest desires are hidden from us by veil upon obscuring veil, of upbringing, of socialization, of personal insecurities and fears, of relationships abusive and abused, of desire habitually unfulfilled and frustrated; and in this sense of “want” in which we want something but for all these reasons do not know what it is, we do not know our own “wills.” For what we will is happiness; and what we really will , whether or not we know it, is whatever it is that will make us happy, but we may not —and all too often do not— know what it is. It is for this reason that the moral life consists in the first place in those practices that enable the discovery of what it is that we really want, the happy life, and the power of insight that leads to that discovery is what Thomas calls prudentia, skill in seeing the moral point of human situations, what true desires are to be met within them. It is then, and only secondarily that the moral life consists in virtuous forms of living, the practices of desire that prudentia has interpretatively uncovered within the maelstrom of desires as actually experienced.
And it is here within his conception of moral practice as desire-discovery— or as he calls it, “practical wisdom”— that for Thomas a principal means of tracing the way back to what we really want, is prayer, oratio. And our only available starting point for that practice of self-discovery is our wants and desires as we actually experience them. Therefore, Thomas says, we ought to pray for what we think we want regardless. For prayer is “in a certain manner a hermeneutic of the human will,” so that by way of placing our desires as we experience them before God we are asking also that those desires be “unfolded,”“explicated,” thereby to release their real significance, the real want that is wrapped up in, “implicated” in all their opacity in their form as experienced. Therefore, says Thomas, we ought to pray, as Jesus did in the garden of Gethsemane, “in response to our animal desire” (secundum sensualitatem). For when we pray as Jesus did then, out of animal need and desire— for Jesus was scared of death, as naturally any animal is— we are placing that animal need and desire within the interpretative power of the divine will itself , wherein alone we will discover our own real will. Therefore, Thomas concludes, we ought always to pray for what we think we want; for Jesus prayed as he did in Gethsemane so as to teach us just that lesson, namely that it is “permitted for human beings naturally to desire even what [they know] is not God's will” and, as if in reinforcement of what for many is a startling thought, he cites the authority of Augustine to the same effect, commenting on the same prayer of Jesus: “It is as if [Jesus] were saying: ‘See yourself in me: for you [too] can wish something for yourself even though God wishes something else.’” Only thus, in the prayer of honest desire, is there any chance of our discovering what are our true desires, our real will.
Denys Turner in Thomas Aquinas: a portrait, (p. 181). Yale University Press.