God is one and does not have any partner in creation. God is Almighty of the world of existence and without Him there is no creator who could bestow existence. God has created all existences small and large and in their creation does not require help of anyone because of a several reasons:
Had there been two gods, it would not have been outside of the domain of the following factors:
That each one of those two gods, as an independent would have created all existences; i.e. each existence would acquire its existence twice and each god would create it directly. With a little pause, the falsehood of this assumption would be proven; because each existence does not have more than one existence and from this consideration cannot have more than one creator. After God had bestowed upon him an existence, it is not possible that another cause too bestows upon him another existence.
Two gods with cooperation and help of each other created creatures in a manner that every creature is created by two gods, and each one of the gods is a part of the cause and half of the doer. This probability too is baseless and void, because if cooperation of these two gods is due to their defect and need, each one of them alone, without help from the other would be helpless and incompetent to create anything, then such defect and incompetency are not compatible with their being god.
And if it is said: each of them alone could create the world but at the same time they cooperate with each other and with the cooperation of each other create existences like some people in lifting a piece of heavy stone cooperate while each one them alone too could lift that heavy stone. This probability too is not correct; because two causes and subjects that could undertake the task alone, if they disregard their independence and seek help from the power of each other and with cooperation and help perform that task, it is not without reason.
Either they want to utilize less energy or want to remain immune from opposition and hindrance of the other. Either they are scared, panic with each other or in summary require help and cooperation of each other. While the need and destitution of any sort does not have an entry about God.
In addition to that since each one these two supposed gods possess knowledge and have power about creation of the world, and his knowledge and power is exactly like his essence, miserliness does not have any entry into His existence, He must be a single and independent cause in creation of the world and in accordance with his knowledge and power should manage it.
That would mean that both of these supposed gods alone and with independence could create the world while it has been proved earlier that the effect of two independent causes in a single consequence is impossible.
The two supposed gods divide world existences between them and each one of them with independence creates a group of existences and interferes in existences created by the other god. Such a probability is also false, because each one of these two supposed gods with respect to existences which happen to be the share of the other god, possess power and knowledge of reformation.
Therefore he should also be the creator and god of them, which requires that two causes must affect a single consequence whose falseness has already been proved. If he does not or is incompetent in creation or is a miser, again he is defective and does not possess the worthiness of being a God.
If one these two supposed gods creates an existence and another one decides to destroy it, if the first god is able to defend his creatures and could prevent the work of another god, the second one is helpless and would not be a god. And if he could not defend his creatures, he is helpless and therefore would not be a god.
Result of Monotheism
Since we believe in the unity of God, and consider Him as Lord of the worlds, other than Him, whoever and whatever it may be, we consider as weak and incompetent. Except God-Almighty we do not consider anyone else owner and worthy of worship and obedience; we do not fall upon the dirt in front of anyone else.
For other than God we do not express servant-hood; we do not give away our freedom and intention under the control of anyone. In front of another human being, we do not perform infinite respect and praise; we consider his appeasement and flattering as a defect.
With regards to Messengers, Imams, and religious leaders we respect them and obey their instructions due to the reason that God has made their obedience as mandatory. Their decrees and instructions always have been under the radius of divine commandments and never transgress from these limits.
We go for the pilgrimages of Messengers and Imams and pay respect toward their tombs, but not with the intention of worshipping a deity, rather with the intention of respect and honor for their spiritual status, infallibility and holiness.
We construct their holy tombs, inhabit them, go for their pilgrimages; in order to pay our tributes for their exalted distinguished position and their religious sacrifices, and in order to make others comprehend that whoever suffered in the path of God and endeavored for the admonishment and guidance of the people would not be forgotten even in this world. In the holy tomb of those pious and selected individuals of God which are a sacred place, offer silent prayers, ask our needs and forgiveness from God, Almighty through the means of placing the sacred souls of those pious individuals as our intercessors.