Gospel Guidebook: Getting and Keeping It Right 
Opinion on Christian Mysticism
The tell tale sign of a Christian Mystic is his or her emphasis on the "inner life" or "higher life." Now, while there are different descriptions and degrees of this "inner life," it usually leads the mystic beyond "What saith the scripture?" (Romans 4:3). For example, Andrew Murray, a Christian mystic who was influenced by William Law, wrote on page 62 of his book Abide in Christ, "Study much to know the written Word; but study more to know the living Word, in whom you are of God." Again on page 64 he wrote, "Remember that the teaching and guidance come not from without: it is by His life in us that the divine wisdom does His work." For me, this kind of advice by Murray sounds dangerous. I think there are certain things, such as technology and knowledge, that God has put a boundary around, and I think we can get into trouble when we venture outside of that boundary, kind of like a child venturing into a "Keep Out" zone in a zoo. When it comes to the things of God and His plans for creatures, I think we need to stay within the boundaries of Scripture.
About 20 years or so ago, I read a book by Jesse Penn-Lewis called War on the Saints. She was a mystic who was influenced by Murray. I am pretty sure she had a role in the emerging church movement in the early 20th century. In her book, she expressed concerns regarding "spiritual life" and the dangers of demonic influence. Her warnings about the risks of introspection and seeking a fastidious righteousness, as well as the dangers of becoming "too spiritual" stuck with me over the years, and as a result, I have always been averse to mysticism and becoming passive during prayer.
Murray, in his introduction to his book Wholly for God, seems to suggest that the Apostle John was a mystic. But to me, this seems wrong. Anything that might superficially appear to encourage mysticism in the Apostle John’s writings is grounded in objective truth, not subjective experience. For example, the famous “abide in me” teaching of Jesus is not an encouragement to seek an inner light and inner life with Jesus, but simply an admonition to keep His commandments and love one another. That this is the true interpretation is explained in the immediate context of the words. These are objective teachings. Similarly, the witness of the Spirit in John's letters is always in close proximity with believing in Jesus, loving one's brother, and living righteously.
Now, I don't mean to downplay all subjective experience. Certainly, we can experience the peace and consolation of the Spirit that makes us cry "Abba, Father," but I just want to say that these experiences come from belief in truth, from within the boundaries of the written Word, godly living, and cultivation of right desires in harmony with God, rather than following some inward light into an unknown and unseen realm.