What, we might ask, is this thing called "temperament," and what relation does it have to character and personality? There are two sides to personality, one of which is temperament and the other character. Temperament is a configuration of inclinations, while character is a configuration of habits. Character is disposition, temperament pre-disposition. Thus, for example, foxes are predisposed -- born -- to raid hen houses, beavers to dam up streams, dolphins to affiliate in close-knit schools, and owls to hunt alone in the dark. Each type of creature, unless arrested in its maturation by an unfavorable environment, develops the habit appropriate to its temperament: stealing chickens, building dams, nurturing companions, or hunting at night.
Put another way, our brain is a sort of computer which has temperament for its hardware and character for its software. The hardware is the physical base from which character emerges, placing an identifiable fingerprint on each individual's attitudes and actions. This underlying consistency can be observed from a very early age -- some features earlier than others -- long before individual experience or social context (one's particular software) has had time or occasion to imprint the person. Thus temperament is the inborn form of human nature; character, the emergent form, which develops through the interaction of temperament and environment.
I want to emphasize that temperament, character, and personality are configured, which means that, not only are we predisposed to develop certain attitudes and not others, certain actions and not others, but that these actions and attitudes are unified -- they hang together. Thus, the Artisans base their self-image on graceful action, bold spirit, and adaptability to circumstance, these three traits evolving together of necessity. Furthermore, these three traits, developing together as if out of a single seed, preclude the emergence of a self-image based on, say, empathy, benevolence, and authenticity, which are characteristics of the Idealists. In the same way, the Guardians base their self-image on reliability, service, and respectability, these three traits emerging together as a unified structure of personality. And again, the unfolding of these three traits together weighs against developing a self-image based on ingenuity, autonomy, and willpower, which is characteristic of the Rationals.