To Robert L. Kroon
Dear Sir, 9 June 1960
There is hardly a psychological statement of which you cannot prove the contrary.
Such a statement as Dr. Eysenck’s can be true but grosso modo, as it is sometimes very difficult to establish the diagnosis with certainty.
As soon as there are symptoms of a neurosis the diagnosis becomes uncertain, as one does not know prima vista whether you are confronted with the picture of the true character or of the opposite compensating character.
Moreover there are not a few introverts who are so painfully aware of the shortcomings of their attitude that they have learned to imitate the extraverts and behave accordingly, and vice versa there are extraverts who like to give themselves the air of the introvert because they think they are then more interesting.
Although I have never made a statistique of this kind I have always been impressed by the fact that pipe-smokers are usually introverted.
The typical extravert is too much of a busybody to bother and fuss with the pipe which demands infinitely more nursing than a cigarette that can be lighted or thrown away in a second.
That does not prevent me from having found heavy cigarette-smokers among my introverts and not a few pipe-smokers among the extraverts, but normally with empty pipes.
Pipe-smoking was in their case one of the cherished introverted mannerisms.
I cannot omit to remark that the diagnosis is not rarely hampered by the fact that it is chiefly extraverts who resent being called extraverts, as if it were a derogatory designation.
I even know of a case where a famous extravert, having been called an extravert, challenged his opponent to a duel.
C.G. Jung Carl Jung, Letters Vol. II, Pages 564-565