…Temperament refers to the mode of reaction and is constitutional and not changeable; character is essentially formed by a person’s experiences, especially of those in early life, and changeable, to some extent, by insights and new kinds of experiences. If a person has a choleric (easily angered) temperament, for instance, his mode of reaction is “quick and strong.” But what he is quick and strong about depends on his kind of relatedness, his character. If he is a productive, just, loving person he will react quickly and strongly when he loves, when he is enraged by injustice, and when he is impressed by new idea. If he is a destructive or sadistic character he will be quick and strong in his destructiveness or in his cruelty.
The confusion between temperament and character has had serious consequences for ethical theory. Preferences with regard to differences in temperament are mere matters of subjective taste. But differences in character are ethically of the most fundamental importance…
In the application of C.G. Jung’s concepts of temperament, those of “introvert” and “extrovert,” we often find the same confusion. Those who prefer the extrovert tend to describe the introvert as inhibited and neurotic; those who prefer the introvert describe the extrovert as superficial and lacking in perseverance and depth. The fallacy is to compare a “good” person of one temperament with a “bad” person of another temperament, and to ascribe the difference in value to the difference in temperament….
Excerpt from Erich Fromm (1947) Man for Himself: An Inquiry into the Psychology of Ethics