According to van Wyhe (2002), 19th-century phrenologists called their interest "the only true science of mind." The basic tenets of phrenology were: (a) the brain is the organ of the mind; (b) the mind is composed of multiple distinct, innate faculties; (c) because they are distinct, each faculty must have a separate seat or "organ" in the brain; (d) the size of an organ, other things being equal, is a measure of its power; (e) the shape of the brain is determined by the development of the various organs; and, importantly; (f) as the skull takes its shape from the brain, the surface of the skull can be read as an accurate index of psychological aptitudes and tendencies. Phrenologists believed that by examining the shape and unevenness of a head or skull, one could discover the development of the particular cerebral "organs" responsible for different intellectual aptitudes and character traits.