• Imagination is strong in a man when that particular function of the brain which enables him to observe is roused to activity without any necessary excitement of the sense. Accordingly, we find that imagination is active just in proportion as our sense are not excited by external objects. A long period of solitude, whether in prison or in a sick room; quiet, twilight, darkness-these are the things that promote its activity; and under their influence it comes into play of itself.

    Arthur Schopenhauer (2012). “Collected Essays of Arthur Schopenhauer”, p.247, Simon and Schuster