In 1920, the young and unknown Heidegger wrote a critical review of Jasper's book “Psychology of Worldviews”. Jasper was impressed by the article and by the young philosopher; and consequently opened himself to him and offered his friendship. In a few years they become very close friends; as they met and discussed philosophy for days at a time. They even planned a new journal where the two of them will take on the philosophy of their time. Their correspondence is full of discussions regarding professors appointments and recommendations in the German university system. Heidegger always met with Jasper and asked for his advice before making any decisions regarding different academic offers. After Heidegger's acceptance of the Nazi's rectorship in 1933, all the communications between the two ceased for more than 10 years. In 1945, Jasper recommended to the denazification committee that Heidegger should be banned from teaching for several years – and this indeed happened. In the same letter, Jasper denounced Heidegger's thinking as some kind of mystical nonsense. They tried to reconnect and forgive each other before dying, but this was no longer possible – as Heidegger refused to acknowledge any guilt and to apologize in private or public. Jasper never fully grasped Heidegger's philosophical project and he was terrified by what he glimpsed from Heidegger's thoughts. In one such final letter, Heidegger criticized Jasper's approach to technology as too simplistic and presented his own understanding of current technology that started with Plato's ideas and in the light of Being. Jasper in turn wrote to Heidegger about old memories, guilt, repentance, and his incomprehension of truth as unconcealment.