Man was not created in jest; He is not immortal, yet he lives for ever. His body is mean and earthly, yet his spirit is divine. When he is purged from carnal passions, he attains to the highest, and in place of being a slave to lust and anger, becomes endued with angelic qualities. The spiritual alchemy which operates this change in man, like that which transmutes base metals into gold, is not easily discovered. This alchemy may be turning away from the world to God, and its constituents are four types of knowledge: the knowledge of God, Self, This World and the Next World. Rebuking those whose piety was only lukewarm or who uttered empty phrases, Imam al-Ghazali explains in these pages how to achieve contentment of the heart, the window into the spiritual world. Originally written in Persian as his own abridgement of his 12th century magnum opus, Ihya Ulum al-Din, this little book is its English version, revised based on an old translation.