Here are some definitions worth remembering, all from The Concise Oxford Dictionary of the Christian Church (E. A. Livinsgtone, ed., Oxford University Press, 1977)
Ascetical Theology: The theological discipline which deals with the so-called ‘ordinary’ ways of Christian perfection, as distinct from Mystical Theology, whose subject is the ‘extraordinary ‘ or passive ways of the spiritual life. It is thus the science of Christian perfection in so far as this is accessible to human effort aided by grace. It also treats of the means to be employed and the dangers to be avoided if the end of the Christian life is to be attained.
Mystical Theology: In Catholic theology, the science of the spiritual life, in so far as this is dependent on the operation of Divine grace. It is commonly contrasted with Ascetical Theology
Mysticism: An immediate knowledge of God attained in this life through personal religious experience. It is primarily a state of prayer, and as such admits of various degrees from short and rare Divine ‘touches’ to the practically permanent union with God in the so-called ‘mystic marriage’. It issues in an increase of humility, charity, and love of suffering. Christian mysticism emphasizes two elements often absent in other religions. In contrast to all pan-cosmic conceptions of the underlying Reality as an impersonal Unity, it recognizes that the Reality to which it penetrates transcends the soul and the cosmos. And in place of all notions of absorption of the soul into the Divine, it posits that the union is one of love and will in which the distinction between Creator and creature is permanently retained. Psycho-physical phenomena, such as trances, visions, and ecstasies, have been frequent concomitants of mystical experience, but they are not held to be essential to it, and are sometimes considered a hindrance to its proper realization. Though Christian thinkers have differed widely in their attitude to mysticism, a measure of it is encountered in the Christian life at its more serious levels in all periods.
Asceticism: The word denotes a system of practices designed to combat vices and develop virtues by means of self-discipline such as are found in many religions. In the NT there are repeated exhortations to self-denial. The theoretical foundation of Christian asceticism was developed by Clement of Alexandria and Origen. Taking over from the Stoics the idea of ascetic action as a purification of the soul from its passions, they saw in it a necessary means of loving God more perfectly and for attaining to contemplation. In the 3rd cent. the ascetic ideal as a way of life spread through Christendom, leading to the age of the Desert Fathers and the beginnings of monasticism in the 4th cent. The monks in both East and West, and later the Mendicant Orders, became the leading representatives of asceticism. At the end of the Middle Ages there was a reaction against the ascetic ideal, esp. among the Protestant Reformers, whose doctrine of the total depravity of man and of justification by faith alone undercut the theological foundation of ascetic practices. The ascetic ideal was, however, upheld in the RC Church of the Counter-Reformation and later. It also played an important role in Methodism and among the Tractarians and their successors.
Acc. to its classical Christian exponents, asceticism is a necessary means of fighting the concupiscence of the flesh; it is also of value as an imitation of the sacrificial life of Christ and as a means of expiation of one’s own sins and those of others. It springs from the love of God and aims at overcoming all the obstacles to this love in the soul.
Personally, I’d never heard the term “ascetical theology” until M became a TA for a class of that name at GTS. In college, one of the things that kept me within Christianity and led me to learn more about was an attraction to Christian mysticism, its practices and experiences. The more that I learned over the years, the more I came to the understanding that Christian mysticism isn’t really something you “do”, rather, it’s something that happens purely as an operation of God’s grace. That having been said, there are things that we do to cultivate within ourselves a receptiveness to all of God’s graces, the mystical ones included. That is, there are paths and practices that we travel that lead us into depths of Christian doctrine, faith, and experience.
To put it another way, is the man on the street who may attend church once or twice a month at the urgings of his family who’d prefer to spend his free time watching football and playing golf less likely to experience mystical graces of God than the cloistered contemplative? My answer is: yes, the first is less likely to experience it—and I offer two explanations. First, as St Paul tells us in the Corinthian and Roman correspondence, we of the Spirit receive different gifts of the Spirit. I believe that these are allotted partly in respect to our authentic selves. The Spirit works through and amplifies who and what we were created to be. A vowed contemplative may well be better suited by both created and granted graces to receive these sorts of experiences. Second—and I believe more important than the first—a primary issue is receptivity: are we open to the possibility of such experiences and do we recognize them for what they are when they happen to us? The man on the street may well receive just as many moments of mystical grace as the contemplative—but may not have the tools and resources to understand what they are and what they mean.
Ascetical theology, then, is the discipline that teaches us actions and ways, paths and systems, that increase our potential for receptivity to the graces of God.
In some ways, given this language, I know recognize that this is what I have been moving towards and captivated by since late high school/early undergrad. Even as a New Testament scholar, my chief area of research is how the demands—and glories—of the biblical texts are enacted, liturgically and practically, in Christian formation. And, in embracing this language, I have found a way to articulate one of the difficulties that I faced as a Lutheran. As a Lutheran I heard over and over again an emphasis on grace and faith—emphases that I embraced and still embrace. I struggled, though, with what seemed to be a deliberate silence around the spiritual disciplines that I encountered among many of the Lutheran clergy and professors I encountered. The fear of Pelagianism and works-righteousness hung heavy over any such discussion. This need not be so, and if we turn to the ascetical masters themselves, this question is treated early and often. An extensive discussion of the topic is found in John Cassian in two places: the first is the polemical Conference 13 (the third conference with Abba Chaeremon) which reacts against a overly or caricatured Augustinian position and the less polemical, more charitable Conference 3 (with Abba Paphnutius). I wonder if I had had the language asceticial theology that I have now if it would have eased my sojourn among the Lutherans (though I doubt it would have changed the eventual outcome).