Just as a belief in the existence of a created thing is not...
Just as a belief in the existence of a created thing is not tantamount to the belief in the plurality of the Divine essence, but is complementary to the belief in the oneness of Allah, similarly a belief in the causation system is not tantamount to the belief in the plurality of creatorship. As the created things are not self-existing, similarly they are not independent with regard to their effectiveness.
As all existing things depend on Allah for their existence and effectiveness, there is no question of the plurality of creatorship. The belief in the causation system is actually complementary to the belief in the creatorship of Allah. It certainly would have amounted to polytheism if we believed that the created things were independent from the viewpoint of their effectiveness, or believed that the relation between Allah and the world was that of a manufacturer and the things manufactured.
A vehicle initially needs a manufacturer to manufacture it, but when it is completed, it operates according to its own mechanism. Even if the maker dies, the vehicle will continue to work. Should we think that the relation of the natural factors, such as water, rain, energy, heat, earth, plants and man to Allah is of a similar nature, as sometimes the Mu'tazilah tends to think, the idea would certainly lead to polytheism.
The created things depend on their Creator for their effectiveness as much as they depend on Him for their origin, existence and survival. The world is His creation and a blessing from Him. It depends on Him totally. Hence the effectiveness of the created things is actually the effectiveness of Allah and their creativeness is His creativeness and an extension of His work.
Even it may be said that to describe the belief that the created things have a role in the affairs of the world as a polytheistic idea, is in itself a polytheistic idea, for it implies an unconscious belief in the independence of the existing things, as is betrayed by the presumption that a belief in their effectiveness will amount to the belief in two centres.
Anyhow, a belief or unbelief in the causation of the things besides Allah is not the line of demarcation between monotheism and polytheism. Is a belief in the supernatural power of an existing thing whether an angel or a man such as an Imam or a Prophet polytheistic, while a belief in the power and effectiveness of a Prophet or an Imam etc. within the normal limits is not so?