In this contribution, the diaries of Johann Georg Widmann and Johann Andreas Manitius are analyzed with regard to the religious and inter-religious motives behind their dialogues with Jews. In spite of their pietistic language and interpretations, the diaries allow a close view at the challenges and conflicts of the dialogues und the underlying images of mutual perception. In contrast to usual philo-Semitic positions on the Christian side, the two travelling 'studiosi' used every possibility of getting in touch with 'real' Jews, sharing their lives and adapting to their spoken language and customs (or - in respect to Manitius - trying to do so). Widmann and Manitius tried to hide their Christian missionary convictions behind seemingly 'Jewish' teachings. This aroused the interest of their Jewish dialogue partners, who obviously perceived the two 'studiosi' not as Jews but as somehow exotic religious specialists. Some of them already knew about the rise of Pietism as new development within Protestant Christianity and tried to find out more about it. Others, already on the way to conversion, made use of the theological knowledge of the two. Regarding the two 'studiosi', on the basis of their adventurous enterprise was the pietistic conviction, that every human being, Lutheran, Catholic or Jew, had to convert from outward, superficial religion (being depraved and legalistic, as explained by St. Paul in relation only to the Jews) to 'true religion', which for them, was true pietistic Christianity and true Judaism at the same time. In spite of this universal moment of thinking (based on millenarian convictions) and the close contact in daily life, it has to be said that there was no discernable development regarding the mutual perception on both sides: The Jewish dialogue partners (apart from the special group of latent converts) did not adapt to the universal view of their partners, whereas the two 'studiosi' did not drop their underlying identification of 'true religion' with pietistic Christianity.