It is striking how differently individuals can react to precisely the same thing. Some love Marmite and others loathe it. And more seriously, many arguments self-perpetuate aside from whether there is evidence or sound reason to decide the issue, because opposing sides embody different temperaments. Depending upon your outlook, Wimbledon is two weeks of poetry in motion, or two weeks of channel-hogging TV tedium. The internet will save civilisation according to the geek, and scramble your brains according to the Luddite. The heavens tell of the glory of God in the eyes of the saint, and of the troubling meaninglessness of empty space for at least some scientists.
Such oppositions struck Jung after his split with Freud. How was it, he asked, that they could interpret psychological problems so differently? The conclusion he reached was that he and Freud exhibited different personality types. The thought led him to a systematic reflection on temperament that is still widely deployed.
Two types seem especially clear: the introvert and the extravert [sic]. An introvert, as Jung was, is more persuaded by the voice of their inner self. An extravert, as he took Freud to be, finds their interest inexorably drawn to external things. "Since we all swerve rather more towards one side or the other, we naturally tend to understand everything in terms of our own type," he explained in Psychological Types, published in 1921. . . .