An essay written with the intention of answering the following questions: how did Jung arrive at formulating his theory? What motivations pushed him to do so? What was Jung’s influence on other typological theories that followed after him and in particular what difference is there between the reworking proposed by Briggs-Myers and Jung’s original theory? Can the Briggs-Myers theory be considered valid or does it represent a distortion of Jung’s original theory? And above all, is the theory of Jungian typologies still considered valid today? Is it still useful? What are its areas of application? Can it be useful in the practical work of the psychologist, counselor and psychotherapist?