Monotheism is the message that all of the Prophets came with.  People then deviated from the truth.  Then Prophet Muhammad, may God praise him, came as the final Messenger and restored true monotheism to humanity.  Below is a detailed explanation of monotheism in Islam. 

Monotheism in Islam

The concept of monotheism (known as tawhîd in Arabic) is the single most important concept in Islam.  Everything in Islam is built upon it.  Islam calls to the absolute oneness of God.  No act of worship or devotion has any meaning or value if this concept is in any way compromised.

Monotheism can be looked at from the following three angles:

1.The Oneness of God in His Lordship

2.Devotion of All Worship to God Alone

3.The Oneness of God in His Names and Attributes

These three angles can be elaborated upon as follows:

The Oneness of God in His Lordship

The oneness of God in His Lordship means that God has complete mastery over the universe in every way.  He alone is the Creator of all things.  He alone causes everything to happen.  He is All-Powerful.  No one shares in His dominion.  None can resist His decree. 

This concept is one that most people on Earth would agree with.  Most people recognize that the Creator of the universe is One and He has no partner.

Devotion of All Worship to God Alone

No one has the right to be worshipped except for God (Allah).  This concept is the central idea that was proclaimed by all the Prophets throughout the ages.  It is the most important creedal belief in Islam.  The purpose of Islam is to call people away from the worship of creation and call them towards the worship of the Creator.

This is where Islam differs greatly from most other religions.  Though most religions teach that there is a Supreme Being who created all that exists, they are rarely free of some form of polytheism with respect to worship.  These religions either call on their adherents to worship other beings as gods besides God (Allah) – though usually placing these other gods on a lower level than the Supreme Being – or they demand that their adherents call on other beings as intercessors between them and God.

All the Prophets and Messengers, from Adam to Muhammad (may God praise them all) called people to worship God alone.  This is the purest, simplest, most natural faith.  Islam rejects the notion of the cultural anthropologists that the early religion of human beings was polytheism, and then slowly the idea of monotheism evolved from that.

The truth is that the natural religion of humanity is to worship God alone.  People later came along and corrupted this religion, introducing into it the worship of other beings.  People seem to have a tendency to want to focus their devotions on something tangible, something imaginable, even though they have an instinctive knowledge that the Creator of the universe is far beyond their imaginations.  Throughout human history, God sent Prophets and Messengers to call the people back to the worship of the One True God, and repeatedly, people returned to the worship of created beings.

God created human beings to worship Him alone.  The greatest possible sin is to worship anyone other than God (Allah).  It is no less sinful if the worshipper intends to get nearer to God by offering devotions to another being.  God does not need intercessors or intermediaries.  He hears all of our prayers and has complete knowledge of everything that happens.

At the same time, God does not need our worship.  He is completely independent of all things.  If every person in the world were to come together to worship God alone, they would not benefit God in the least.  They would not add an atom’s weight to His dominion.  Conversely, if all creation abandoned the worship of God, this would not decrease His dominion in the least.  By worshipping God, we benefit our own souls and fulfill the purpose for which we were created.  We do not fulfill any need of God.  He is needless.

The Oneness of God in His Names and Attributes

The oneness of God (Allah) in His names and attributes implies that God does not share in the attributes of created beings, nor do they share in any of His.  God is unique in every way.  Muslims believe in all of the attributes that God asserts for Himself and that His Prophet ascribes to Him with the understanding that those attributes are not the same as the attributes of created things.  Likewise, we negate any name or attribute for God that God and His Messenger negate for Him.

God’s attributes are all attributes of perfection and completeness.  Human deficiencies cannot be ascribed to God.  God has no deficiency or weakness whatsoever.

It is a form of polytheism to ascribe to God attributes of created things.  It is likewise a form of polytheism to ascribe to created things attributes that belong to God alone.  Anyone who believes that another being is, for instance, All-Knowledgeable or All-Powerful has committed the sin of polytheism, which is the greatest of all sins in Islam.