The present volume contains lectures given by Rudolf Steiner in Berlin, Cologne, Düsseldorf, Hamburg and Lugano in 1905 and 1906. It follows on directly from volume GA 90a, which contains the Berlin lectures to members from 1903 and 1904.
The lecture from January 10, 1906 in Lugano was included in this volume because it is close to the other lectures in this volume in terms of time and subject matter, and the other unpublished member lectures from 1906 are already reserved for other volumes (e.g. GA 111).
Often it is no longer possible to determine whether the notes were taken at Branch's lectures, at Rudolf Steiner's talks in smaller circles, or even at private lessons for individuals. Presumably, in the early days of Rudolf Steiner's theosophical work, the boundaries were also fluid.
Rudolf Steiner developed the majority of the topics covered in this volume simultaneously or later for his written work. Particular reference is made here to:
- Mysticism in the dawn of modern spiritual life and its relationship to the modern world view (1901, GA 7)
- Christianity as a Mystical Fact and the Mysteries of Antiquity (1902, GA 8)
- Theosophy: An Introduction to Supersensible World Knowledge and the Human Condition (1904, GA 9)
- How to Know Higher Worlds (1904-1905, GA 10)
- From the Akasha Chronicle (1904-1908, GA 11)
- The Stages of Higher Knowledge (1905-1908, GA 12)
- Lucifer-Gnosis, fundamental essays on anthroposophy (1903-1908,GA 35)
| I. | On the Root-Races of Atlantians and Aryans | January 1, 1905 |
| II. | Elemental, Sidereal and Heavenly Deities — Human Development and the Zodiac | January 2, 1905 |
| III. | The Deification of Man – The Task of the Arts | January 15, 1905 |
| IV. | The Apocalypse and Theosophical Cosmology I | January 30, 1905 |
| V. | The Apocalypse and Theosophical Cosmology II | February 6, 1905 |
| VI. | The Apocalypse and Theosophical Cosmology III | February 13, 1905 |
| VII. | The Apocalypse and Theosophical Cosmology IV | February 20, 1905 |
| VIII. | The Apocalypse and Theosophical Cosmology V | February 27, 1905 |
| IX. | The Apocalypse and Theosophical Cosmology VI | March 6, 1905 |
| X. | Easter and Theosophy | April 21, 1905 |
| XI. | The Sermon on the Mount | June 19, 1905 |
| XII. | About the Gospel of John | June 26, 1905 |
| XIII. | The Seven Principles | August 18, 1905 |
| XIV. | Subjective — Objective Dharma In Karma | August 20, 1905 |
| XV. | Spiritual Science as a Source of Healing | October 9, 1905 |
| XVI. | Self-knowledge and Knowledge of God | October 16, 1905 |
| XVII. | The Relationship of Occultism to the Theosophical Movement | October 22, 1905 |
| XVIII. | Theosophy in Daily Life | October 30, 1905 |
| XIX. | Theosophy and the Concept of Freedom | November 6, 1905 |
| XX. | Knowledge of the Higher Worlds I | December 11, 1905 |
| XXI. | Knowledge of the Higher Worlds II | December 18, 1905 |
| XXII. | Knowledge of the Higher Worlds III | December 28, 1905 |
| XXIII. | The Apocalypse of John I | January 16, 1905 |
| XIV. | About the Book of Genesis | January 17, 1905 |
| XV. | On the Significance of the Catholic Mass in the Sense of Mysticism | March 17, 1905 |
| XVI. | On Planetary Evolution | March 18, 1905 |
| XVII. | The Apocalypse of John II | March 19, 1905 |
| XVIII. | Novalis's Novel in Prose, “Heinrich Von Ofterdingen” | April 26, 1905 |
| XXIX. | Yoga and Unio Mystica | April 27, 1905 |
| XXX. | The Sermon on the Mount | December 2, 1905 |
| XXXI. | On the Concept of God | January 19, 1905 |
| XXXII. | On the Life of a Spiritual Seeker | January 20, 1905 |
| XXXIII. | The Old Norse Sagas of the Gods | March 22, 1905 |
| XXXIV. | Yoga | December 4, 1905 |
| XXXV. | The Days of the Week — Sibylline Wisdom | April 9, 1905 |
| XXXVI. | The Spiritual Development of Man | October 15, 1905 |
| XXXVII. | On German Mythology | December 10, 1905 |
| XXXVIII. | The Transient and the Eternal | January 10, 1906 |
