Each new discovery declares to man the existence of an endless number of unknown elements. Could anyone say that this vast world of existence, all of the parts of which either separately or in unity and interconnection bear witness to an infinite knowledge and power, need not have a creator and cold have come into being without reason and cause? Or could it be said of these particular and universal domains or order and equilibrium, and finally of this total cosmic order which through innumerable interrelations has made the world a single unit running its course according to laws which know no exceptions, that all this has occurred without plan and only through accident and chance? Or could anyone say that each of the phenomena and domains in the cosmos has chosen for itself, before coming into being? Or could anyone claim that this world, which is a single unit and which possesses complete unity, harmony and the interconnection of parts, could be the result of multiple and different commands issuing from different sources?
Obviously, an intelligent man, who relates every event and phenomenon to a cause, and who sometimes spends long periods in investigation and efforts to gain knowledge of a cause that is unknown to him, will never accept the possibility of a world existing without a Being as its cause. Such a person, who by observing a few bricks placed upon one another in an orderly manner considers them to be the effect of an agent possessing knowledge and power and who denies the possibility of chance and accident in the putting of the bricks together and therefore concludes that a plan and purpose must have existed beforehand, will not regard the cosmic order as being the result of an accident or the play of chance.
A deeper awareness of the order reigning in the world is enough to show that the world, along with the order reigning over it, is the creation of an omnipotent Creator who has brought it into being through His limitless knowledge and power and who directs it toward an end. All the partial causes which bring about individual events in the world ultimately end in Him. They are in every way under His dominance and are guided by His wisdom. Everything that exists is in need of Him, while He has need of nothing and does not depend on any causes or conditions.
God, the Exalted, says, "Lo! in the heavens and the earth are portents for believers. And in your creation, and all the beasts that He scattereth in the earth, are portents for a folk whose faith is sure. And the difference of night and day and the provision that Allah sendeth down from the sky and thereby quickeneth the earth after her death, and the ordering of the winds, are portents for a people who have sense. These are portents of Allah which we recite unto thee (Muhammad) with truth. Then in what fact, after Allah and His portents, will they believe?" (Quran, XLV, 3-6).
Every reality in this world which we can possibly imagine is a limited reality, that is, one whose actualization depends upon certain necessary causes and conditions. If these do not exist that reality cannot exist in the world. Every reality has a boundary beyond which it cannot extend its existence. Only God is such that He has no limit or boundary, for His reality is absolute and He exists in His Infinity no matter how we try to conceive of Him. His Being does not depend upon and is not in need of any causes or conditions. It is clear that in the case of something limitless we cannot conceive of multiplicity, for any supposedly second reality will be other than the first, as a result of which each would be limited and bound and would set a boundary to the reality of the other. For example, if we consider a limitless volume we cannot conceive another limitless volume alongside it. And if we do suppose another, it will be the same as the first. Therefore, God is one and has no partner.
We have already mentioned the Bedouin who approached Ali in the middle of the fighting during the Battle of the Camel and asked if he asserted that God was one. In answer Ali said, "To say that God is one has four meanings: Two of those meanings are false and two correct. As for the two incorrect meanings, one is that one should say ’God is one’ and be thinking of number and counting. This meaning is false because that which has no second cannot enter into the category of number. Do you not see that those who said that God is the third of a trinity [i.e., the Christians] fell into infidelity? Another meaning is to say that so and so is one of this people, namely a species of this genus or a member of this species. This meaning is also not correct when applied to God, for it implies likening something to God and God is above all likeness.
"As for the two meanings which are correct when applied to God, one is that it should be said that God is one in the sense that there is no likeness unto Him among things. God possesses such uniqueness. And one is to say that God is one in the sense that there is no multiplicity or division conceivable in Him, neither outwardly nor in the mind nor in the imagination. God possesses such a unity." (Bihar al-anwar, vol. II, p. 65)