The angel of Jehovah, the flame of fire, and the bush, are all within the consciousness of man. The bush is a nerve center through which the universal life energy runs like electricity over a wire, making a light but not consuming. In mental activity there is a vibratory process that uses up nerve tissue, but in the wisdom that comes from the heart this "bush" or tissue is not consumed. The light of intuition or flame of fire burns in the heart, yet there is no loss of substance. The angel is the presiding intelligence always present in every life action or function.
Man is first attracted by the phenomenal side of spiritual things; then, when he gives his attention for the purpose of knowing the cause, the Lord reveals Himself. When Moses began to investigate, he found that he was on holy ground. The forces of Spirit at the center of man's body are so intense that the outer consciousness cannot stand the current and hold itself together. Absolutely pure in essence, this inner fire must be approached by pure spiritual thought. Removing the shoes is symbolical of taking from the understanding all material concepts.
Another explanation of the burning bush is: the burning bush, which was not consumed, represents spiritual life's contacting substance. Divine life, spiritual fire, does not consume; it purifies and renews substance.