Carl Freiherr du Prel (1839 - 1899), philosopher, writer, and occultist, advocated for a spiritual renewal, to which he aimed to contribute by establishing a transcendental psychology. The core of his views was the recognition of the unconscious, which manifests in dreams, trance, clairvoyance, and telepathic suggestion, but is usually hidden as the shadow side of consciousness. Against this backdrop, he dealt with such occult phenomena and was thus one of the forerunners of parapsychology. The work presented here addresses topics such as the mental activity of the artist, telepathy, clairvoyance, what are premonitions?, automatic writing, among others. This is a reprint of the original edition from 1894.