The oneness of God in Islam

We witness a superbly flawless plan in the universe-can it be without a planner? We see great enchanting beauty and harmony in its working-can they be without a creator? We observe wonderful design in nature-can it be without a designer?
We find that the universe is like a superbly written, fascinating book-can it be without an author?
"O, Mankind: worship your Lord, Who created you and those before you, so that you may ward off evil; Who has made the earth a resting-place for you, the sky a canopy and Who causes water to pour down from the heavens, thereby producing fruits as food for you. So do not set up rivals to God, when you know better. (Quran 2:21-22)
This is the basic tenet which Prophet Muhammad (peace be upon him) asked humanity to adhere. It is an important metaphysical concept and answers the riddles of the universe. It points to the supremacy of law in the cosmos and the all-pervading unity behind the manifest diversity.
It presents a unified view of the world and offers the vision of an integrated universe. After centuries of groping in the dark, man is now coming to realise the truth of this concept, and modern scientific thought is moving in this direction.
 But it is not merely a metaphysical concept: it is a dynamic belief and a revolutionary doctrine. It means that all men are the creatures of one God and that they are therefore all equal. Any discrimination based on colour, class, race, or territory is unfounded and illusory. It is a remnant of the days of ignorance that chained men down to servitude. Humanity is one single family under God, and there can be no sanction for those barriers. Men are one - and not bourgeois or proletarian, white or black, Aryan or non-Aryan, westerner or easterner. Islam gives us a revolutionary concept of the unity of mankind.
The Prophet came to unite humanity on the word of God, which says: "Cling firmly together by means of God's rope and do not be divided. Remember God's favor towards you when you were enemies; He united your hearts so that you became brothers because of His favor. (Quran 3:103) 
The starting point of Islam is the belief in the Oneness of God (Tawhid).
The second part is that God has not left man without any guidance for the conduct of his life. He has revealed His guidance through His prophets, and Muhammad (peace be upon him) was the last prophet. To believe in a prophet means to believe in the revelation that he has received, to accept the law that was transmitted to him by God, and to follow the code of conduct that he was instructed to pass on to humanity.
Every prophet of God, according to the Quran, strove to build man's relationship with God on the principle of His sovereignty.
Every one of them said: "I am to you God's apostle, worthy of all trust. So be committed to God, heed Him, and obey me." The guidance is revealed through the prophets.
It is a part of their mission to translate it into practice in their own lives and in the society they try to reform. All of the prophets are representatives of God, but they are human beings and their lives are models for mankind.
Prophet Muhammad (peace be upon him), since he was the last prophet, is the final model for mankind.
(The writer is a former KT staffer)