 Another issue is whether dreams are subject to the will (Ichikawa 2009). Imagination is often characterized as active and under our control (Wittgenstein 1967: 621, 633), involving “a special effort of the mind” (Descartes 1641: VI, 2), whereas perception is passive. Because dreams just seem to happen to us without being under voluntary control, they present an important challenge for the imagination view. Ichikawa (2009) argues lucid control dreams show dreams are generally subject to the will even where they are not under deliberate control.