This series of lectures on the science of spiritual knowledge begins by addressing an audience in Dornach, Switzerland, where only months earlier his architectural masterpiece, the first Goetheanum, had been destroyed by fire. He discusses the nature of our solar system, revealing the planets characterized by freedom and those that determine destiny. Spirits of the Moon live in seclusion, preserving "original wisdom" and reflecting powers connected to sexuality, whereas the Sun creates harmony. Jupiter is "the thinker," whereas spirits on Saturn act as "living memory." Speaking in London, Steiner states that what happens to people in sleep is more important than anything that happens while we are awake. He asserts that we must learn to see ourselves as images of spirits and spiritual activities on Earth. Returning to Dornach, Steiner breaks with the theme and reports on his recent visit to England and Wales, where he attended an educational conference in Ilkley, a summer school in Penmaenmawr, and a school for the disadvantaged in the London East End. Steiner speaks of the particular atmosphere he experienced in West Yorkshire and North Wales, where remnants of Druid spirituality live in the surroundings. The latter theme emerges strongly in following lectures, which examine the Druid priest's Sun initiation and perception of Moon spirits. The Druids investigated secrets of the universe, influencing both social and religious life. He also describes the mythic being of Woden, who signified the birth of intellectuality and the subsequent fear of death, which he asserts can be healed by the Mystery of Golgotha. In the final section, Rudolf Steiner discusses the past, present, and future development of the human mind. Again, he discusses the importance of Druid culture, noting that the ground plans of the stone circles in Penmaenmawr are similar to that of the first Goetheanum. He also points to the crucial roles of the ancient mysteries and Christ's deed in human development.