Source: At-Tawhid or Monotheism, P.22-24, by: Ayatullah Misbah Yazdi
One of the most simple and most easy to understand degrees of At-Tawhid is At-Tawhid in creation, namely, that one believes that the world of being has been created by One Creator. This belief existed even among the polytheists. The Holy Qur`an quotes from the polytheists of Maccah and the idolaters who were during the life-time of the Holy Prophet (s.a.w) of Islam as having said that concerning their idols they did not believe in creation, rather, they regarded the idols as a means for drawing near to the One God and said:
... ما نعبدهم الّا ليقربونا الي اللّه زلفي ...
“... We do not serve them except that they may make us nearer to Allah, ... (39:3).”
The idolaters imagined that the Almighty Allah, has daughters named the angels (God forbid) and with this imagination, they made imaginary physical portraits for them and worshipped them so that the souls and lords of those idols would be pleased and as a result they would intercede with the One God (for the idolaters).
In another ayah the Holy Qur`an says:
و لين سألتهم من خلق السموات و الارض ليقولن اللّه ...
“And if you ask them who created the heavens and the earth, they will certainly, saw ‘Allah’... (31:35).”
So, the Polytheists of Maccah did not deny Allah, rather they believed in gods lower than the level of the One God and worshipped them by making their idols. They believed that gods hold the power and authority over the world and that the affairs of the world are managed according to their view, ie, it is they who are effective in the revolution of the moon and the sun, in the emergence of the earthly and heavenly phenomena and in men's felicity and adversity, that some were in charge of the management of the seas, some others had undertaken the responsibility for the land, that some had supervision over the affairs of the wars and some managed the affairs of the men. Theses polytheists considered the world to have numerous directors and believed in Lords of the species. And this is the matter against which the Holy Qur`an has contested most severely. And, the Holy Qur’an clarifies to the people that the same One Who is the Creator of the world is also the (One) Lord and the Manager of the world and that none can cause any effect or change in His creatures without His permission.
With this explanation, it becomes clear that in Islam mere belief in the Oneness of the Creator is not sufficient and that Islam does not consider those who have such beliefs to be monotheists and worshippers of Allah The One and Only, rather, At-Tawhid in Lordship (belief in One Lord) should also be added to belief in One Creator.