Contrary to a common stereotype, mystical thought has always played a role in the development of Christian thought, just as it has in other religious traditions. While eschewing Gnosticism, Neoplatonist pagans such as Plotinus were used by Christian writers, and the Pseudo-Dionysius’ writings could be called mystical works from a Christian perspective. The Eastern Orthodox Church has emphasized contemplation, and this trend became dominant during the late states of the Eastern Roman Empire just before Constantinople was taken by the Turks in 1453. In the Western Church, St. John of the Cross, St Julian of Norwich, and St. Theresa of Avila were only a few of the great mystics. The Church has taken care regarding mysticism, not in order to make life difficult for the mystics, but to make sure that the teachings of the mystics were in line with Christian teaching. St. Theresa of Avila gladly submitted to that rule and did not begrudge it–anyone with doubts should read her writings. There were a few exceptions, but this was not due to the authors’ mysticism. The problem was the teachings of certain mystics seemed to conflict with the teachings of Christianity. I am not sure if Scotus Erigena was a mystic, but he was clearly a pantheist, and while not formally condemned, his position was stronger than the alleged panentheism of Meister Eckhart–Erigena clearly identified God with the universe in his dynamic pantheistic system. Meister Eckhart, on the other hand, believed, as far as I can follow his thought, that the was a good Thomist–if every contingent thing that exists is radically dependent on God, then without God all contingent things are literally no-things. Thus God is all in all. Eckhart’s teachings could be a form of panentheism, and one could even interpret them in terms of classical theism. In my judgment, Eckhart’s heresy trial was based on a misunderstanding of his teachings.Mystics tend to emphasize the untiy of all things in the One, and sometimes they seem to subsume creation into God so that God is the only reality and contingent things are unreal. R. C. Zaehner has argued that Christian mysticism always kept the God-world distinction in the background while Eastern mysticism did not. That is a widely disputed point; many writers would claim there is a strong cross-religious and cross-cultural commonality to religious experience. Huston Smith has argued that within a religious tradition that approves their use, psychedelic drugs may be a way to reach the transcendent. From a very different perspective, Stanislav Grof has argued that high doses of LSD can put some persons in contact with transcendent reality. Even the majority of mystics who do not use drugs use fasting, chants, and other methods to focus the mind. However, as William James notes in his Varieties of Religious Experience, there is a passivity to mystical experience–ultimately it is a gift of grace. James is also correct in noting the ineffable quality of mystical experiences. It is not that mystics cannot communicate anything about their experience–otherwise, why would they write books about mysticism–but that language does a poor job in communicating the experience. In December 1273, St. Thomas Aquinas told his secretary that he had a mystical experience of God of such power that everything he had written before was “straw.” He died shortly afterward in March 1274.
Mystics also have a sense, as James noted, of certainty that the experience they had was real. The experience itself does not last long; James is probably not far off the mark when he states that most experiences last less than half an hour. These special gifts of grace are the height of the contemplative (Mary-type) life as opposed to the more practical Martha-type life. The church requires both.
Christian mystics should always keep in mind the fact of the incarnation (as did St. Theresa of Avila). Matter is good and redeemed by God through Christ. Any mystical experience that denies the goodness of matter is heretical from a Christian perspective. What mystical experience tells Christians, among other things, is how small we human beings are in comparison with God. Even the Beatific Vision will not result in anything close to a complete knowledge of God. It is good for humans, who have a tendency toward pride and arrogance, to realize their smallness, their nothingness, in the face of Existence Itself.