... much seemingly chance variation in human behavior is not due to chance; it is in fact the logical result of a few basic, observable differences in mental functioning.

By developing individual strengths, guarding against weaknesses, and appreciating the strengths of other types, life will be more amusing, more interesting, and more of a daily adventure than it could possibly be if everyone were alike.

Extraverts ... cannot understand life until they have lived it. Introverts ... cannot live life until they understand it.

They [INTJs] are likely, however, to organize themselves out of a job. They cannot continually reorganize the same thing, and a finished product has no more interest. Thus, they need successive new assignments, with bigger and better problems, to stretch their powers.

We cannot safely assume that other people's minds work on the same principles as our own. All too often, others with whom we come in contact do not reason as we reason, or do not value the things we value, or are not interested in what interests us.

[On Jung's theory of psychological types:] My mother, Katharine C. Briggs, introduced it into our family and made it a part of our lives. She and I waited a long time for someone to devise an instrument that would reflect not only one's preference for extraversion or introversion but one's preferred kind of perception and judgment as well. In the summer of 1942 we undertook to do it ourselves.

the present Western civilization ... is dominated by the extravert viewpoint. There are plenty of reasons for this domination: extraverts are more vocal than introverts; they are more numerous, apparently in the ratio of three to one; and they are accessible and understandable, whereas the introverts are not readily understandable, even to each other, and are likely to be thoroughly incomprehensible to the extraverts.