According to the theoretical system of carl gustav jung (1875–1961), the ego has four inseparable functions (i.e., four different fundamental ways of perceiving and interpreting reality): thinking, feeling, sensation, and intuition. Thinking is the opposite of feeling, and sensation is the opposite of intuition. Jung suggested that most people start life developing one of these four ego functions and at various stages throughout life may develop others. The undeveloped ego functions have less effect on the individual’s cognition.