This text about Dutch Arabist and scholar of Islam Prof. Dr. Johannes (Hans) G. Jansen (1942-2015) is based on Cornelis Hulsman’s personal experiences with Prof. Jansen as a student at Leiden University, the Netherlands, but even more on the email exchanges with Hans Jansen in 2008 and between August 1, 2011, and April 5, 2014. Jansen developed a highly negative image of Islam while Hulsman advocated dialogue with Muslims. Neither of them was able to convince the other person about the views they developed throughout the years. Jansen’s emails have been presented in Dutch with Hulsman’s English translation while Hulsman’s correspondence is only presented in English translation. Jansen’s emails provide a unique insight in his thinking about Islam, his lack of confidence in dialogue with Muslim scholars, his belief that presenting texts in a wider context would dilute the danger he saw in Islam and his sources, mostly anti-Islamic authors such as Raymond Ibrahim and Robert Spencer, as well as his polemics and sarcasm in discussions. Most of his emails concerned links to articles he believed to be worth reading which underlined his own convictions. His email correspondence shows how much he had been impacted by his studies of extremist thought and how this had made him radically anti-Islam.