Allah, ta^ala, said in the Qur’an:
[ أفي الله شكّ ]
Ayah 10 of Surah Ibrahim means: {There is no doubt about the existence of Allah.}
The first obligation on the mukallaf person is to know about Allah, ta^ala. Allah is the Creator of all the existent things and is the One Who manages all the creation. If, with our sound mind, we carefully think about all the creations and ponder about their existence, we must know that they have a Creator Who created them.
The mental proof that Allah (God) exists:
With the sound mind, we know irrefutably that every writing has to have a writer, the act of hitting has to have a hitter, and that a building has to have a builder. Therefore, it follows that this universe with all the creations in it has to have a creator Who is Alive, attributed with Will, Knowledge, and Power, and this is Allah. He is clear of all imperfections. He is the One Who does not resemble any of His creations, and nothing resembles Him. The sound mind does not accept the existence of an action without someone who carried it out.
It is not conceivable for nature to be the Creator, because nature has no will. So, how would nature create? It is also not permissible for something to create itself. Finally, something cannot create something that resembles it.
For example, the child is born small; he does not talk or walk. Then he develops. He starts gradually and slowly to talk and walk. Then he matures and becomes a young man, then middle-aged, then old, after which he dies. Who changed him and transformed him from one state to another? Allah is the One Who created and changed him, and willed for him to die.
A story of a man who denied the existence of Allah:
It is related that a man who denied the existence of the Creator came once to one of the caliphs and told him: "The scholars of your time say that there is a creator for this universe, and I am prepared to prove to them that this universe has no creator."
The caliph sent for one of the top scholars telling him of the man's claim and ordering him to come. The scholar was purposely late; then he came. The caliph welcomed him and seated him in the center of the session. Present at this meeting were many scholars and important people. So the man said: "Why were you late in your arrival?" The scholar said: "What if I tell you that a very strange matter occurred to me, and because of it I was late? My house is behind the river of Dijlah (Tigris). I came to cross the river, but I did not find anything other than an old boat with broken planks. When my gaze fell onto it, the planks moved, came together, and reassembled so that the boat became seaworthy. All this happened without the work of a carpenter or a worker. I sat in it, crossed the river, and came to this place.”
The man said: "O people, listen to what your scholar says. Have you heard anything more absurd than this? How can a boat exist without a carpenter to build it? This is an explicit lie."
The scholar said: "O blasphemer, if the mind does not accept the existence of a boat without a builder or carpenter, then how do you say that this entire universe exists without a creator?" The man became silent. He was refuted.
