Intuitive gnosis or mystical knowledge is different from conventional sensual or rational knowledge. This knowledge is not achieved through theoretical contemplation but is attained through remembering God, meditation, purification of soul and mystical life. In this knowledge there is no distance or medium between the object and subject of knowledge. In other words, the knower and the known or the witness and witnessed enjoy a kind of unity or union and connection. Hence, this knowledge is known as direct, intuitive and without medium. The subjects of this gnosis are God, universes of being and inner and hidden worlds which, in the viewpoint of mystic, are nothing but the divine inner manifestations. As our ordinary knowledge is diverse and gradational, mystical intuition too is diverse and gradational. As our ordinary perceptions are divided into sensual and rational, our mystical discoveries are divided into formal and spiritual.From the perspective of Islamic mysticism, the superior path to gnosis of God and faith in Him is intuitive knowledge. There are two criteria for assessment of mystical institution, particularly for non-mystics, i.e. reason and revelation. The main thrust of the present paper is to sum up the viewpoints of the Muslim mystics about this issue.