This book presents a detailed explanation of the classical Islamic concept of God's unity as it relates to faith and acts of religious devotion. It also discusses the major areas within which the Islamic unitarian belief (tawheed) is either nullified or compromised by idolatrous concepts collectively called shirk. The uniqueness of this work lies not only in its thorough treatment of the subject in a fluid and uncomplicated English style, but is also unique in its modern presentation of classical theological issues. True faith of a standard acceptable to Allah has to be based on tawhid free from shirk, as stated in the Qur'an and ahaddith and outlined in detail in the preceding chapters. Anything less than that represents an aspect of idolatry and or disbelief, regardless of how firmly those who join partners with God profess their faith in Him or how skillfully they rationalize their unsanctioned practices. Allah's unity must he maintained spiritually, intellectually, and practically in all facets of human life within which the pleasure of God is sought. Monotheism, as brought by the Prophets of God, was not merely a theory to be philosophically appreciated or emotionally championed, but a pragmatic blueprint for human existence in submission to the will of Almighty God, Allah. The significance of this fact lies in the purpose of man's creation. Allah said: "I only created the jinn and man for my worship" (Qur'an 51: 56). The creation of man is itself a manifestation of Allah's perfect attributes. He is the Creator (al-Khaliq), and thus man was brought into existence from non-existence. He is the Most Merciful (ar-Rahman), and thus the pleasures of this world were granted to him. He is the Most Wise (al-Hakeem), and thus He prohibited the substances and acts which are harmful to man while allowing those which are not. He is the Most Forgiving (al-Ghafoor),