 Kant initially preferred “influx” theories of soul-body relations to the “parallelist” theories of occasionalism and pre-established harmony, but he eventually decided that dualism was incoherent. Already in the Measurement of Living Forces, he was grappling with the problem of the location of the soul and the nature of its action. Anatomists had long speculated that some region of the brain, e.g., the pineal gland (Descartes 1650) or the corpus callosum (Euler 1763), was the site of interaction between soul and body. For a time, Kant seems to have believed that souls were positioned in space and could act outside themselves and be acted upon by bodies. Later he became convinced that souls were not localized in space, though they could effect changes, deciding that that neither medicine nor metaphysics could illuminate the question. He denies that we can understand the entry of the soul into body at conception or its relation to the body throughout life, or its exit and separate existence after death. Because all our experience is experience of ourselves as living beings — when soul and body are bound together — we cannot know what a separated soul would experience. Leibniz compared existence after death to a deep sleep or a swoon, but to investigate these matters is, Kant says, like standing before a mirror with your eyes closed to see what you look like when you are asleep (20:309).