After his retirement in 1980 he became a Christian pacifist, and intensified his work on the conceptual definition of quantum physics, particularly on the Copenhagen interpretation.
Setelah pensiunnya pada 1980 ia menjadi seorang pasifis Kristen, dan mengintensifkan pekerjaannya dalam definisi konseptual tentang fisika kuantum, khususnya tentang Interpretasi Kopenhagen.