Animal self (Latin for soul = anima). Lower brain and spinal column. Unchangeable self. Tightly linked to the body. Registers bodily pleasure and bodily pain. (Pain is an abstraction, rather than something materially measurable. Thus the pain of suffocation is not literally equivalent to the CO2 molecules in the blood, but rather corresponds to the nerve impulses set up by the CO2 sensor in the lower brain. Configuration of lower brain is equivalent to the soul. Nerve impulses produced by lower brain in response to sensing high CO2 level in blood stream is an example of the soul's functioning.) Soul is partly determined by genetics, partly by early childhood programming or social conditioning. Unlike spirit, soul cannot be changed after this early childhood programming is complete. Soul thus constitutes the fixed point in the universe, whereas matter (including the body) and spirit are mutable.