General Mental Proof of the Existence of the Creator:
The Islamic scholars mentioned that every accountable person is obligated to know the General Mental Proof about the Existence of Allah. An example of this is, if one says: writing must have a writer, the building must have a builder, and the writing and building are part of this universe.  Hence, the whole universe must have a Creator Who brought it into existence, and Who does not resemble this universe in any way.  Another example is for the person to say: I did not exist; now I exist after I was not.  Whatever exists after not existing must have some One Who brought him into existence. This One must Exist without resembling anything. Similarly, all the other parts of the universe need a Creator.

Detailed Mental Proof of the Existence of the Creator:
The Islamic scholars said that it was a communal obligation upon the Muslims to know it. An example of how someone goes about this proof is for someone to say that all the parts of this universe are (originated) events (have a beginning).  This universe consists of two things: entities and properties. An entity is something that stands on its own, and a property is something that stands within an entity.  An example of an entity is you and I. An example of a property is color and motion. Entities are not without properties. These entities are either in motion or at rest. This is an obvious intuitive matter. Properties like motion and stillness are events (have a beginning) because by the happening of one, the other goes away. When motion starts, stillness ends, and vice versa. The one which started has a beginning because it just started, and the one which ended also has a beginning because it just ended. If something was not an event, i.e., eternal, it would not come to an end. The fact that something starts states that it is possible for it to come to an end. Thus, the One Who does not have a beginning does not have an end.

The entities are themselves events because they are associated with properties that have a beginning.  Whatever has an attribute with a beginning must itself have a beginning. This is so, because if this was not true, this person is really saying that this entity does not exist. The people of the truth said enough to refute such a claim. The example they gave is: If one says: I will only give you a dollar today if I have given you a dollar yesterday, and I will not give you that dollar unless I had given you one before it, and so on without a beginning, will you ever get this dollar? The answer is no. Claiming there are events without a beginning implies that there are no events today. However, since the events are happening today, they must have had a beginning. Consequently, it is clear that the entities and properties have a beginning.  Hence, the whole universe has a beginning.

Obviously, whatever has a beginning needs someone else to bring it into existence, and this One must do so with a Will.  It is not valid mentally for the world to have existed by chance, because the mind says that it is impossible for something to exist without someone bringing it into existence. This is because there are two options: existence and non-existence. One of these two options will not outweigh the other on its own.

Additionally, it is clear that the world could not have created itself. This is because if a person says Joe created himself, he is saying Joe created Joe. If Joe were the creator, Joe existed before Joe, and if Joe were the created, Joe existed after he did not exist. Hence, Joe would exist and not exist at the same time, and this is impossible. It becomes a circular argument. Joe’s existence depends on Joe’s existence while he is not existing.

It is also impossible for nature to have created the world, because nature does not have a will. In order to create, one must specify entities with properties, and this requires a will. If someone says: nature created the world, we ask him to define nature. If he says the whole world, we already covered this. If he said part of the world, like the trees for example, then if the whole world could not have created itself, then part of it could not have created the world either.

Hence, the One who brought the world into existence must be without a beginning, because if He did have a beginning, we go back to previous argument. If the Creator had a beginning, then some one may say: who created him? and who created the one who created him, and so on?. This leads to saying that events have no beginning, which was disproved earlier in the example of the dollar.

The true creed is that this world must have a creator, who is supremely powerful and is attributed with Knowledge and Will, it is indeed Allah, the lord of the worlds. Nothing deserves to be worshipped except God (Allah) and Muhammad is the last messenger of Allah.

Allah knows best.