Quran 10:39. Nay, they deny that; the knowledge whereof they could not compass and whereof the interpretation has not yet come unto them. Thus those before them did deny. Then see what was the end of the Zâlimûn ! Dr Umar Al-Ashqar, the author of the book, 'The World of Jinn and Devils' cites the above verse in order for us to appreciate the underlying reason for the denial of the existance of jinn. Many people deny the world of unseen because they are not able to comprehend as to the nature of the unseen or there is a lack of detailed explanation regarding some matters of the unseen. One may, as such, bear in mind the underlying reason (or one of the many) for the denial or distortion with regards to Allah's names and attributes (as done by the Jahmiya, Mutazila or Ashariyya). Many such people, when presented with the verses regarding Allah's names and attributes, come up with the counter argument that we must not understand the verses on their apparent meaning. They justify their position by saying, 'describe a hand for me'. Since, in their understanding at least, a hand must be like that of a human being - one cannot designate such attribute to Allah. They impose a pre-condition that one must be able to explain Allah's attributes before believing in their apparent. As the precise nature or description of Allah's attributes may not be found in the Quran and Sunnah - they want to seek an easy way out to justify their denial or distortion of the attributes; instead of saying, 'we believe'. Allah knows best.