The Qur'an and Hadith refer to the heart as an organ of understanding, thinking and feeling. This book begins by examining the 'intelligence' of the heart according to the Qur'an and hadith and shows how science is only now beginning to discover what has been known to Muslims for over 1400 years. Recognising that the key to Eternal life is a Pure Heart, the second part of the book examines the main diseases of the heart and their cures according to Islam.