The Akasha Chronicle is a writing which preserves everything that has ever occurred. But it is not really a writing in the ordinary physical meaning, for it consists of images. You see, for example, Caesar in every situation of his life, — you do not see what he has done, but the inner impulses which led him to his deeds. These Akasha pictures possess a high degree of life, and if we cannot interpret them in the right way, they can give rise to great delusions.
The source of many spiritistic aberrations is, for example, the appearance of an Akasha picture at one of these seances. If you summon Goethe, and the Akasha picture of November 25th 1797 appears before you, giving you information concerning some question, this picture will reply as Goethe would have replied had he been asked that question on November 25th 1797. Only those who really know the spiritual world can judge whether they are dealing with a reality or with a shadow.
Source: Rudolf Steiner – GA 100 – Theosophy and Rosicrucianism: Lecture IV: Man’s Further Destinies in the Spiritual Worlds – Kassel, 19th June, 1907