In the case of a solar eclipse, the evil that has spread over the earth can be carried out into the cosmos to wreak more havoc there, whereas in the case of a lunar eclipse, people who absolutely want to be possessed by evil thoughts can receive them from the cosmos.' In the first full translation of this lecture course, Rudolf Steiner implores his audience to recognize the connections between the material and spiritual worlds. Eclipses of the sun and moon, for example, are 'forces at work in the universe, just like those we study today in the clinic or in the chemistry or physics laboratory'. Even everyday thinking can have a strong impact on the outer world. Materialistic thought, he says, can quite literally atomize our surroundings: 'if all human beings start to think that everything has to be explained in terms of atoms... then the earth will actually turn into atoms... these false ideas create false realities...' Steiner speaks of the 'world of will' as being three-dimensional, the 'world of feeling' as two-dimensional, and the 'world of thinking' as one-dimensional. The ego itself is dimensionless, and only inner, living thinking can grasp the spiritual-mental. He discusses key cultural figures such as Friedrich Nietzsche, Herman Grimm and Julian the Apostate, and introduces multiple additional topics, including the effect of planetary forces on humans; the healing impacts of metals and other substances; the revitalization of thinking through meditation and concentration; the effects of the separation of science, art and religion; and the necessary transition from philosophy to anthroposophy.