Firstly, by the way we have spoken of the varying relations of the sun and moon to the earth, seeing in them the effects of certain astral activities, we have treated them as if they were of like nature, namely, resulting from a movement of the relevant heavenly body round the earth. According to the Copernican conception, however, only the moon rotates round the earth, whereas the apparent yearly progression of the sun is actually caused by the earth's motion round the sun. This raises the question of how far the Copernican, heliocentric aspect is valid in a science which strives to embrace the astral realm of the universe in its inquiries.