According to saint John of Damascus, Islam is one of the Christian sects. The difference between Islam and Christianity is mainly in understanding Logos (Logos as an eternal Word of God) and “logias” – the words of God that were revealed and written down. Christians understand Logos as the eternal Word of God directed to people by God. This Word is Jesus Christ. Meanwhile, Muslims refer to Jesus as a prophet and teacher. The Word of God for them is Koran, but initially it was also the Holy Bible. Muslims could not comprehend the person of the Holy Spirit and perceived Him only as a Divine power. Nevertheless, the biggest problem for Muslims living at the time of John of Damascus was to understand the embodiment.