Why
Allah?

There is more than one God in the cultures of the earth, so why believe in Allah specifically?

There is no worshiped god in all the religions on the earth except Allah.
Our disagreement with all the world religions is that they have worshiped with Allah other gods such as Jesus and the Holy Spirit in
Christianity, Vishnu, Shiva and Brahma in Hinduism...etc.
All religions believe in Allah the One and Only God, and they deem Him the Creator of the existence.
But they just worship alongside Allah other gods.

Even the idols of the polytheists were not worshiped as deities for their own selves, for they acknowledged that Allah is the Creator, but they make them intermediaries to Allah. {If you ask them who created the heavens and earth and subjected the sun and moon, they will surely say, “Allah.” How are they then deluded?} [Surat al-‘ Ankabūt: 61] Shaykh al-Islam Ibn Taymiyyah (may Allah have mercy upon him) said: “And whoever thinks that the idols worshipers believed that idols create the world or that they send down rain, grow plants, or create animals or otherwise, then he is ignorant about them. Rather, they worshiped these idols for the same reason the polytheists worshiped the graves.” 
Will Durant says that the origin of pagan Hinduism ultimately goes back to the belief in the One God. He says about the Hindu gods: “These thousands of gods represents the same model of the Christian churches that hold thousands of figures as saints. A Hindu never thinks, even for a single moment, that such uncountable gods have supreme sovereignty.”

A report submitted to the British government in India during the British occupation of India stated: “The general conclusion reached by the committee from the research is that the overwhelming majority of Indians hold a firm belief in one Supreme God.” Allah is One in all religions of the earth. {and our God and your God is One,} [Surat al-Ankabūt: 46] Idols and human gods are nothing but intermediaries to Allah that are heresy. {As for those who take others as guardians besides Him, [saying], We only worship them so that they may bring us closer to Allah.} [Surat az-Zumar:3]

It is silly to think that need is matched by absurdity!

In fact, need is matched by wisdom, not absurdity. A rich and reputable doctor may treat people without needing anything from them but treats them for their own benefit. Here we do not describe his action as absurd! Wisdom and a great intent behind the act do not revolve around the need/absurdity cycle!

Moreover, a swimmer may rescue a child out of mercy, then leave him and go without waiting for the child’s parents to thank him. Here, his action is not classified as a need or absurdity, rather, this is a generous act, a noble purpose, and of good character! So, need and absurdity are not necessarily correlated. According to Sahīh Muslim, Allah Almighty said in a Qudsi Hadīth: O My servants, were the first of you and the last of you, the human of you and the jinn of you to be as pious as the most pious heart of one of you, it would not increase in My dominion anything. O My servants were the first of you and the last of you, the human of you and the jinn of you to be as wicked as the most wicked heart of one of you, it would not decrease from My dominion anything. It is but your deeds that I count for you and then recompense you for them. So, whoever finds good, let him praise Allah, and whoever finds other than that, let him blame none but himself.”

Allah is free from need of the worlds. Our endeavor, effort, and work are only for ourselves. {Whoever strives, he only strives for his own good. Indeed, Allah is in no need of the worlds.} [Surat al-Ankabūt: 6]

We know that Allah has wisdom in all of His creation, even if we are ignorant of it, and the patient’s ignorance of the doctor’s wisdom does not mean that the doctor’s decisions are absurd. Knowledge of divine wisdom does not require understanding all dimensions of wisdom, but it is sufficient to understand some of them! It is sufficient for us to know that we are charged with worshiping Allah and know that there is a divine wisdom. This is sufficient for us in general; otherwise, we are like those who disbelieve in all that they do not understand {But they rejected that which they did not comprehend, and its warning has not yet been fulfilled against them.} [Surat Yūnus: 39] Allah is Wise and He created us for a wise purpose, may He be Exalted.

He alone is the one truly worthy of worship, no one else deserves to be worshiped except Allah; the Creator who brought us into existence out of nothingness. He said: {O mankind, worship
your Lord, who created you and those before you, so that you may become righteous;} [Surat al-Baqarah: 21] He is the One who guided us, the One who legislated, decreed, commanded and prohibited. {His is the creation and the command} [Surat Al-A’rāf: 54] It is not just the creation that belongs to Allah, but the command as well belongs to Him. We obey His commands; glory be to Him.

Worship is the right of Allah due upon the slaves. He, The Almighty created us, gave us life, gave us sustenance, guided us and sent His messengers to us so as to test us as to which of us is the best in deeds. So, worship is Allah’s right due upon us. {He is the One Who created death and life to test you as to which of you is best in deeds, and He is the All-Mighty, the Most Forgiving.} [Surat al-Mulk: 2].

Our worldly life and that of the Hereafter will not be set aright except with worship, nor will our morals be reformed except with it; for worship prevents immorality and evildoing, and with it the worldly life will be reformed. Our Lord, the Almighty said: {Recite [O Prophet] what is revealed to you of the Book, and establish prayer, for indeed prayer restrains one from
immoral acts and wickedness.} [Surat al-Ankabūt: 45] We will attain Paradise only through worship, as it is salvation in the Hereafter and bliss in the worldly life.

Worship is for us and for our own good, and it is obligatory upon us towards Allah Almighty because He is our Creator, and its benefit returns to us only, and negligence affects us only.
Paradise is expensive, so whoever desires Paradise should work for it. We need Allah Almighty...We need to worship Him, whereas He is Free of need for us and for all His creation.

How do we know Allah?

We know Allah by numerous ways, out of which we mention here only four:

First way: We know Allah through the sound natural disposition.
Man is disposed to know that he has a creator. You know by nature that you have a creator who created you in this form, with such organs, fashion and amazing perfection.
Also, man by his nature knows that he is required to resort to his Creator through worship, and also knows that he needs his Creator, Glory be to Him, at all times, and this feeling of need for Allah increases in adversity.

All mankind is disposed to know Allah by nature, Allah Almighty said: {Adhere sincerely to the true religion in all uprightness. This is the natural disposition with which Allah has created mankind. There is no change in Allah’s creation. This is the straight religion, but most people do not know.} [Surat ar-Rum: 30].

He also said: {And [remember] when your Lord brought forth from the loins of the children of Adam their offspring and made them testify about themselves [asking], Am I not your Lord? They said, yes; indeed, we testify. [We did so] lest you should say on the Day of Resurrection, “we were unaware of this,} [Surat Al-A’rāf: 172].

Before we were created, we were naturally disposed to know Allah and be His slaves. {and He made them testify about themselves [asking], “Am I not your Lord?” They said, “yes; indeed, we testify.”}.

The Prophet (may Allah’s peace and blessings be upon him) further said in Hadīth whose authenticity is acknowledged by Al-Bukhāri and Muslim: ‘There is no child born except that he is born with a sound natural disposition.

We are all born on that natural disposition, which is sufficient for every person who seeks the truth to guide him to the truth, and that he should submit to that truth once he finds it.

This disposition cannot be denied even by the staunchest people in terms of disbelief, especially in difficult times. In fact, all people resort to Allah in hardships and forget about all what they associate with Him in worship. {When hardship strikes you at sea, you forget all those whom you invoke besides Him. Then when He brings you safe to the land, you turn away.
Mankind is ever ungrateful.} [Surat al-Isrā: 67].

When a person is in severe distress and feels that destruction is imminent, he invokes no one but Allah and forgets about all his polytheistic beliefs. This sincere invocation to all in adversity is prompted by the sound natural disposition every person has within him.

Eisenhower – one of the American presidents – who was a commander of American forces in World War II, said after witnessing how the forces return to the natural disposition at the time of great danger: “There are no atheists in the trenches.

In the trench during war, there is no one who denies Allah, they all return to Him. This is the true natural disposition that all mankind admit in times of adversity.

The second way to know Allah is reason: We know Allah by reason.

Allah Almighty said: {Were they created by none, or were they the creators [of themselves]?} [Surat at-Tur: 35]
According to reason, there are three possibilities that have no fourth: The first possibility: We are created without a creator {Were they created by none} which is impossible, for how can we be created without a creator?

The second possibility: We created ourselves {or were they the creators [of themselves]}, which is impossible as well, for how can I create myself before I am created?

Then, according to reason, there remains the third possibility, and it is the one that the noble verse did not mention as it is self-evident. It is that we have a creator that created us.
So, we know Allah by reason.

The third way to know Allah is to reflect on His creation:

Contemplating the creation of Allah puts us in front of the greatness of Allah, the Exalted. {Say, look at what is in the heavens and earth.} [Surat Yūnus: 101]

The more we ponder on the subtle creation of Allah and the amazing perfection, the more our knowledge of Him increases.

This is what we have previously mentioned in the context of the proof of bringing into existence and the proof of providence and perfection.

The fourth way to know Allah is through the messengers:

This is the best way through which we know Allah, the Exalted. It is to know Him through His messengers and prophets. The messengers told us about Allah and about His attributes and essence. Through the prophets we get to know Allah with His names and attributes and know how to worship Him and draw close to Him. We know how to be saved from the punishment of Allah on the Day of Reckoning. Messengers called people to worship Allah, in other words, they called them to return to their natural disposition on which they were created, and to worship Allah as He commanded.

Messengers guided the people to the way of truth and salvation: {These messengers were sent as bearers of glad tidings and as warners, so that the people may have no excuse before Allah after [the coming of] the messengers. For Allah is All-Mighty, All-Wise.} [Surat an-Nisaa?: 165].

So prophets and messengers informed us about Allah and Allah’s support was given to them through miracles which leaves no one with an excuse with Allah on the Day of Resurrection.

That is because Allah, the Exalted, gave you a natural disposition with which you can know your creator, gave you reason, gave you eyesight, so that you can ponder on His creation, and sent to you messengers. Thus, there is no excuse for you before Allah.

There are many religions

Why Islam?