Freud was alarmed by Jung’s letter. Jung’s interest in synchronicity and the paranormal rankled the strict materialist; he condemned Jung for wallowing in what he called the “black tide of the mud of occultism.” Just two years earlier, during a visit to Freud in Vienna, Jung had attempted to defend his beliefs and sparked a heated debate. Freud’s skepticism remained calcified as ever, causing him to dismiss Jung’s paranormal leanings, “in terms of so shallow a positivism,” recalls Jung, “that I had difficulty in checking the sharp retort on the tip of my tongue.” A shocking synchronistic event followed. Jung writes in his memoirs:
While Freud was going on this way, I had a curious sensation. It was as if my diaphragm were made of iron and were becoming red-hot — a glowing vault. And at that moment there was such a loud report in the bookcase, which stood right next to us, that we both started up in alarm, fearing the thing was going to topple over on us. I said to Freud: ‘There, that is an example of a so-called catalytic exteriorization phenomenon.’ ‘Oh come,’ he exclaimed. ‘That is sheer bosh.’ ‘It is not,’ I replied. ‘You are mistaken, Herr Professor. And to prove my point I now predict that in a moment there will be another such loud report! ‘Sure enough, no sooner had I said the words that the same detonation went off in the bookcase. To this day I do not know what gave me this certainty. But I knew beyond all doubt that the report would come again. Freud only stared aghast at me. I do not know what was in his mind, or what his look meant. In any case, this incident aroused his distrust of me, and I had the feeling that I had done something against him. I never afterward discussed the incident with him.