Rudolf Steiner: "We say to ourselves: ‘Our gaze falls upon the rainbow which emerges as if out of the bosom of the surrounding universe; in looking at it we look into the macrocosm, into the great world; the macrocosm gives birth to the rainbow.’ Now let us turn our gaze inward; within ourselves we can observe that out of a vague, unthinking brooding, there emerge specific thoughts relating to something or other — in other words, thought flashes up within our souls. It is an everyday experience; we have only to see it in the right light. Let us take these two things, the macrocosm which gives birth to the rainbow out of the bosom of the universe, and the other thing, that in ourselves thought is born out of the rest of our soul-life. Those are the two facts of which the wise men of ancient Greece already knew something and which men will come to know again through spiritual science. The same forces which cause thoughts to light up in our microcosm call forth the outward rainbow from the bosom of the universe. Just as the Demeter forces from without enter into man and become active within, so outside us in the cosmos those forces are active which form the rainbow out of the ingredients of Nature; there they work spread out in space; within, in the microcosmic world of man, they cause thought to flash up out of the indefinite. Of course ordinary physics has not yet come anywhere near such truths — nevertheless, that is the truth.
Everything that is outside in space is also within us. Today man does not yet recognize the complete harmony which exists between the mysterious forces at work in himself, and the forces active outside in the macrocosm; indeed he probably regards that as a fantastic daydream. The ancient Greek could not say what I say today about these things, because he could not penetrate the matter with intellect; but it lived in his subconscious, he saw it, or felt it clairvoyantly. If today we wish to express in up-to-date phraseology what the Greek felt, we must say that he felt working within him the forces which caused thought to flash up, and felt that they were the same forces which organized the rainbow without. That is what he experienced. And he said to himself: ‘If there are psychic forces within me which cause thought to flash up, what is it that is without? What is the spiritual force in the widths of space, above and below, right and left, before and behind? What is it outspread there in space which causes the rainbow to flash up, causes the sunrise and the sunset, causes the glimmer and the glory of the clouds, just as within me the forces of the soul bring forth thought?’ For the ancient Greek it was a spiritual being who gave birth out of the universal ether to all these phenomena — to the roseate tints of sunrise and sunset, to the rainbow, to the glimmer and the glory of the clouds, to thunder and lightning. And out of this feeling, which, as I said before, had not become intellectual knowledge, but was elemental feeling, there arose the intuitive perception: ‘That is Zeus!’ One does not get any idea, still less any sense of what the Greek soul experienced as Zeus, if one does not approach this experience and this feeling by way of the spiritual-scientific outlook. Zeus was a being with a clearly defined form, but one could not get an idea of him without the feeling that the forces which cause thought to light up in us are also at work in what flashes up externally, such as the rainbow and so on. But today in anthroposophical circles, when we look into the human being and try to learn something of the forces which call forth in us thoughts, ideas — the forces which call forth all that flashes up in our consciousness — we say that all this constitutes what we call the astral body. In this way, having the microcosmic substance, the astral body, we can give an answer in terms of spiritual science to the question we have just put in a more pictorial way, and we can say that as a microcosm we have in us the astral body; we can then ask ourselves what corresponds without in the widths of space to the astral body — what fills all space right and left, behind and before, above and below? Just as the astral body extends throughout our microcosm, so is the universal ether, so are the wide expanses of space, permeated with the macrocosmic counterpart of our astral body, and we can also say that what the ancient Greek pictured to himself as Zeus is the macrocosmic counterpart of our astral body. In us we have the astral body: it causes the phenomena of consciousness to light up; without extends the astrality from which, as from the cosmic womb, is born the rainbow, the sunrise, the sunset, thunder and lightning, clouds and snow. The man of today can find no word to cover what the Greek thought of as Zeus, and which is the cosmic counterpart of our astral body."