Apperception (from the Latin ad-, "to, toward" and percipere, "to perceive, gain, secure, learn, or feel") is any of several aspects of perception and consciousness in such fields as psychology, philosophy and epistemology. Meaning in philosophy The term originates with René Descartes in the form of the word apercevoir in his book Traité des passions. Leibniz introduced the concept of apperception into the more technical philosophical tradition, in his work Principes de la nature fondés en raison et de la grâce; although he used the word practically in the sense of the modern attention, by which an object is apprehended as "not-self" and yet in relation to the self. Immanuel Kant distinguished transcendental apperception from empirical apperception. The first is the perception of an object as involving the consciousness of the pure self as subject – "the pure, original, unchangeable consciousness that is the necessary condition of experience and the ultimate foundation of the unity of experience". The second is "the consciousness of the concrete actual self with its changing states", the so-called "inner sense" (Otto F. Kraushaar in Runes). Transcendental apperception is almost equivalent to self-consciousness; the existence of the ego may be more or less prominent, but it is always involved. See Kantianism. The German philosopher Theodor Lipps distinguished the terms perception and apperception in his 1902 work Vom Fühlen, Wollen und Denken. Perception, for Lipps, is a generic term that covers such psychic occurrences as auditory and tactile sensations, recollections, visual representations in memory, etc. But these perceptions do not always hold one's conscious attention – perception is not always consciously noticed. Lipps uses the term apperception, then, to refer to attentive perception, wherein, in addition to merely perceiving an object, either one also consciously attends to the perceived object or one also attends to the very perception of the object. Meaning in psychology In psychology, apperception is "the process by which new experience is assimilated to and transformed by the residuum of past experience of an individual to form a new whole". In short, it is to perceive new experience in relation to past experience. The term is found in the early psychologies of Herbert Spencer, Hermann Lotze, and Wilhelm Wundt. It originally means passing the threshold into consciousness, i.e., to perceive. But the percept is changed when reaching consciousness due to its entry into an already present interpretive context; thus it is not perceived but