.... It was observed that some people, in the way in which they consciously seek direction and adjustment in their lives, are almost exclusively guided by objects of the external world. Facts and, circumstances, the opinions and feelings of other people, and ideas in current use, determine the adaptations which these people make to life. When in difficulty, they seek support first of all from the external world. Jung calls these people outwardly directed, or extraverted types. Another group of people are guided, in so far as conscious motives are concerned, by entirely different factors; they are primarily conscious of their own subjective reactions to events. They are peculiarly sensitive to these—to what they feel, how they think, about any situation.
Where these reactions conflict, they seek to weld them into some sort of harmony of attitude and opinion. In their adjustment to life they thus take as starting-point their own needs and the demands of their own being. They also consult these when in difficulty, and for this purpose they withdraw into themselves. For this reason Jung called them inwardly directed, or introverted types.
A closer investigation shows us that we are here dealing, not with different character-structures, but with typical habits of emphasis, for in everyone we find both forms of adjustment, and it is impossible to say that the one form remains entirely unconscious while the other prevails in consciousness. Under certain conditions, everyone will consciously direct himself towards the external world, while under other conditions he will turn to himself for counsel. Introverted and extraverted states occur in everyone. The only difference is the fact that one person will feel more at home in the one state, while another will find the other more familiar. The extraverted individual will feel much more secure when in contact with other people than when alone. If he reflects too long by himself, everything becomes more confused than if he can guide himself by the opinions of others. The extravert will therefore prefer to maintain contact with others for as long as possible, and if he should find himself in an introverted state, he will soon escape from it. The reactions of others assume more precise and more differentiated forms in his consciousness than do his own.
With introverts, it is exactly the opposite. For them the introverted state is the safest and most agreeable. Alone with himself, the introvert knows exactly what he wants. In contact with others, he loses his sense of security. He finds it an overwhelmingly difficult task to assert himself and to express himself properly. When alone, he feels himself at ease; and when forced into contact with the external world, he has no regrets when the contact is broken and he may withdraw into himself once more. Since an individual of this type is more intensively in touch with himself than with others, he will know his own intentions relatively better than those of other people, and the activities of his own ego will be more differentiated in his mind than those of the external world....