Mankind, in general, has maintained a belief in the existence of the Creator of the universe since time immemorial.

The duty of the prophets of Allah was not so much to inform their people of Allah’s existence as to warn them against associating others with Him, and to teach them how to serve Him:

Their messengers said, “Is there any doubt concerning Allah, the originator of the heavens and the earth?” (Ibrahim 14:10)

The early Muslim scholars did not even have to address the issue of the existence of God, for it was a blatantly obvious fact, which nobody questioned. It was only around the fourth Hijri century, when people’s doctrine started being infiltrated with atheism and permeated by unbelief, that the scholars had to address the issue.

The existence of Allah is established by various types of proofs, which may be conveniently classified under four categories.

Scriptural

The major religions of the world have scriptures, which teach the existence of the Creator. In particular, the Qur’an, the only revealed book which has remained totally intact and preserved, establishes the existence of Allah by compelling rational arguments, while at the same time serving as an enduring miracle testifying to His reality. It decisively establishes His uniqueness and non-resemblance to creation, and emphasizes that worship is only for Him.

Fitrah

As already mentioned, human beings have an inherent and inborn recognition of their Creator. This is a consequence of a pledge which Allah took from the soul of every one of us before we came into this world. In the Qur’an, He says:

And [mention] when your Lord took from the children of Adam – from their loins – their descendants and made them testify of themselves, [saying to them], “Am I not your Lord?” They said, “Yes”. (Al-A`raf 7:172)

Every human being is born with this natural disposition, which is called in Arabic “fitrah”. Abu Hurayrah reported that the Messenger of Allah (peace and blessings be upon him) said, “Every child is born upon fitrah, then it is his parents who make him Jewish, or Christian, or Magian (Zoroastrian), just as an animal delivers a perfect baby animal; do you find it mutilated?” (Al-Bukhari)

But, this fitrah sometimes becomes latent, especially when the human being is in a corrupt and spiritually degenerate environment, which is devoid of reminder and exhortation towards the Lord. Fitrah surfaces, however, in times of calamity and distress. How many avowed atheists find themselves raising their hands to the skies in supplication when in affliction? And how do the staunch unbelievers cry out for deliverance when they are faced with death?

It is He who enables you to travel on land and sea until, when you are in ships and they sail with them by a good wind and they rejoice therein, there comes a storm wind and the waves come upon them from everywhere and they assume that they are surrounded, supplicating Allah, sincere to Him in religion, “If You should save us from this, we will surely be among the thankful.” (Yunus 10:22)

Yet, this sincerity is often short-lived:

But when He saves them, at once they commit injustice upon the earth without right. (Yunus 10:23)

Mankind is all too apt, during the course of their daily life of comfort and enjoyment, to forget their Lord:

And when some trauma touches man, he calls to his Lord, turning repentant to Him. Then, when He grants him a favor from Himself, he forgets that for which he called to Him before, and sets up partners to Allah. (Az-Zumar 39:8)

It is to awaken and alert this fitrah that God, in His mercy and wisdom, sent messengers to remind people of their true religion, and to direct them towards fulfilling their commission of serving their Lord. Almighty Allah has ordered His prophet to proclaim:

Say, “O mankind! If you are in [any] doubt regarding my religion, then [know that] I do not worship those whom you worship besides Allah, but I worship Allah Who will take your souls (at death): I am commanded to be (in the ranks) of the Believers.” (Yunus 10:104)

The specific mention of death here drives home the stark reality, which even the pagans must concede to when faced with the glaring, intuitive evidence, that Allah alone causes death. The rational individual, then, should prepare for this inevitability by responding to his Lord.

Islam is merely a hearkening by man to his nature, an acceptance of that which is naturally good and intuitively right:

So, set your face toward the religion in uprightness. That is the fitrah of Allah, upon which He has created mankind. Let there be no changing of Allah’s creation. (Ar-Rum 30:30)

There are others who stubbornly resist this truth and reject God’s message when it is presented before them, although they are well aware of its veracity. This was the attitude of Pharaoh and his supporters; and its consequences are severe, in this world and the hereafter:

They rejected [Our signs], although their own souls were convinced of their truth, out of iniquity and arrogance. See, then, what was the sequel for those who cause corruption! (An-Naml 27:14)

Yet, even hardened deniers who stand in the way of truth and resist it may grab hold of it at the last moment, before it is too late, for on account of the surfacing of the fitrah, a disbeliever who is faced with death on the battlefield may suddenly embrace Islam. The Muslim who fights in Jihad will similarly be exposed to death frequently, thus enhancing and sharpening his awareness of Allah.

Rational

It is intuitively obvious, and confirmed by science, that the universe had a beginning. Every action requires a doer, and thus the existence of creation necessarily indicates the existence of the Creator. Allah appeals to the human mind and rationality, saying (Were they created from nothing, or are they [themselves] the creators?) (At-Tur 52:35). Quite obviously, we have been created and brought into existence after being non-existent, and it is also plain that we do not create ourselves.

A few years ago, the sands in the Empty Quarter desert, in the Arabian Peninsula, were blown away by a windstorm to reveal the ruins of a city that had been covered by the sands. Scientists began to examine the contents of the city in an attempt to determine the period in which it had been built. Nobody among the archaeologists or others even suggested that this city could have appeared as a result of the natural actions of the wind, rain, heat and cold, and not by the actions of man. If anyone had suggested such a thing, people would have regarded him as crazy and would have taken pity on him. So how about if someone had said that this city was formed by the air from nothing in the far distant past, then it settled on the earth?

Having recognized the necessity of the existence of a Creator, one then realizes that there can only be one Creator:

If there were in [the heavens and the earth] gods other than Allah, [the heavens and earth] would surely have been disordered. (Al-Anbiya’ 21:22)

Allah has not taken a son, nor is there any god with Him, for in that case, each god would assuredly have championed that which he created, and some of them would surely have overcome others. Glorified be Allah above that which they allege! (Al-Mu’minun 23:91)

Further, this one and only Creator cannot possibly resemble creation:

Is, then, He Who creates, like he who does not create? Do you not reflect? (An-Nahl 16:17)

Perceptual

We witness and experience the answering of prayers, and this in itself indicates the existence of Almighty Allah, Who says (When you sought help of your Lord, and He answered you.) (Al-Anfal 8:9)

Al-Bukhari and Muslim narrated a hadith in which a Bedouin asked the Prophet (peace and blessings be upon him) to pray for rain, since crops were perishing and people were starving. The Prophet prayed to Allah for rain, and almost immediately clouds began to gather and it began raining heavily. Also in this category of evidence are the miracles which people witness at the hands of the prophets, such as the splitting of the moon and the enduring miracle of the Qur’an, which served to support Prophet Muhammad.

Finally, we should bear in mind that abundant as the proofs may be, they are only of avail to those who honestly and sincerely search for the truth. As for those obdurate ones who simply refuse to believe, they will not cease their idle disputation:

And they say, “Our hearts are in a covering from that to which you call us, and in our ears is a deafness, and between us and you is a veil, so act, we [also] are acting.” (Fussilat 41:5)

Those against whom the decree of your Lord has been verified will not believe, although every sign should come to them, until they see the painful punishment. (Yunus 10:96-97)

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Taken with modifications from onislam.net. Originally published on islamweb.net.