Von Hartmann's "Philosophy of the Unconscious" has been the subject of many different estimates, but is regarded as having less intrinsic than historical value. Its influence upon other thinkers was especially marked during the years following its first appearance, but by the early 20th century that influence had much decreased. However, there are some grounds for considering it as providing the connection of thought between Schopenhauer's philosophy of the 'Will' and Sigmund Freud's psychology of the 'unconscious'. In a sense his thought creates the bridge between the post-Kantian views of Will (in particular Schopenhauer's) and the Zürich school of psychology.