writes, “is as remote from our conceptions and apprehensions, as that of spiritual substance or spirit; and therefore, from our not having any notion of the substance of spirit, we can no more conclude its non-existence, than we can, for the same reason, deny the existence of body.” Just as we form the complex idea of bodies by supposing their qualities, such as figure and motion, or color and weight, to co-exist in some substratum; so by supposing the activities we find in ourselves—such as “thinking,