Ascetic and Mystic and their derivative nouns asceticism, mysticism though not true synonyms are not always clearly distinguished, partly because of overlapping implications but largely because the first two are often applicable to the same person.
Historically many of the great mystics have been ascetics. But ascetic suggests an austere mode of life in which everything that does not. contribute to or may interfere with the end in view (usually spiritual or sometimes intellectual perfection) is sacrificed, and certain acts (as fasting and mortification) are practiced not for their own sake but for their disciplinary effect especially in strengthening one’s powers of contemplation.
Mystic, on the other hand, suggests the possession of a power (as a high capacity for contemplation) or of an inner revelation, by means of which one overpasses the limits of human reason and by spiritual insight comes to a knowledge of that which is divine or supernatural.
Ascetic and mystic, therefore, when applied to the same person, regard him from different points of view; the former implies that he practices austerities believed favorable to spiritual contemplation; the latter, that he has had the mystical experiences that are the end of contemplation. But the two terms do not necessarily imply each other; ascetic, even when applied to those who aim at spiritual perfection, does not connote attainment of mystical knowledge; mystic, on the other hand, does not in itself imply a connection with an ascetic life.
Although asceticism and mysticism may denote doctrines or practices, their chief differences are apparent when they denote the theory upon which such doctrines and practices are based.
Asceticism often designates the theory that abstinence from otherwise lawful acts or pleasures and the practice of austerities are conducive to spiritual and intellectual perfection; mysticism, the theory that immediate knowledge of God or ultimate reality is attainable through a faculty that transcends the reason and makes no use of ordinary human perceptive or ratiocinative powers.
- one is sometimes tempted to think that to approve mysticism is to preach asceticism. Certainly many mystics have been ascetic. But that has been the accident of their philosophy and not the essence of their religion
—Ellis