Occult Science is Rudolf Steiner's term for the ancient Way of Initiation, and in this book he shows that an objective description of the spiritual experience, (one quite as balanced as the findings of external science), is both possible and attainable. Material scientists pour scorn on the idea of other spiritual worlds, but it is unreasonable to expect that instruments of gross matter will ever detect the highly attenuated spiritual dimensions. Originally published in 1910.
Source and copyright Global Grey Ebooks: https://www.globalgreyebooks.com/index.html. The book can be downloaded from the Global Grey website.