I.
The evidence for the existence of Allah, may He be Exalted, and His oneness, and that He is the Creator and Controller, is innumerable. It includes man himself and what is seen in him of the brilliant creation of Allah. It is quite clear that man did not create himself, and that ignorant nature did not create him; rather he was created by a wise and all-knowing Creator Who is in control of the universe. Hence Allah, may He be Exalted, says:
{Or were they created by nothing, or were they the creators [of themselves]?
Or did they create the heavens and the earth? Rather they lack certainty of faith } [At-Tur 52:35, 36]
And He says:
{ And on the earth are signs for the certain [in faith]
And in yourselves. Then will you not see?} [Adh-Dhariyat 51:20-21].
For more information on the evidence for the existence of Allah, see the answer to question no. 26745.
II.
Any debate with an atheist should start from this point, which is proving the existence, wisdom and knowledge of Allah. Then you can explain the wisdom behind the creation of man and why he was brought into being, which is so that he will worship Allah and obey Him, as Allah says:
{And I did not create the jinn and mankind except to worship Me.
I do not want from them any provision, nor do I want them to feed Me.
Indeed, it is Allāh who is the Provider, Lord of Might, the Powerful} [Adh-Dhariyat 51:56-58].
Allah, may He be Exalted, has decreed that the life of this world is to be a life of trials and tests, as He says:
{Blessed is He in whose hand is dominion, and He has power over all things –
[He] who created death and life to test you [as to] which of you is best in deed - and He is the Exalted in Might, the Forgiving} [Al-Mulk 67:1-2].
These trials and tests result from people being of different levels of good or evil, faith or disbelief, poverty or wealth, and strength or weakness.
The people of faith, who are successful, submit to the command of Allah, respond to the call of His messengers, and show kindness to His creation.
The people of disbelief and disobedience stubbornly reject the truth, rebel, commit sins and mistreat others.
Allah has promised those who believe and obey Him eternal bliss and the supreme triumph in the gardens of paradise, and He has warned those who disbelieve and commit sin of hell and punishment in the hereafter.
What happens in this life of oppression, evil and corruption is part of the trial and test. If Allah willed, He could destroy the disbeliever and the wrongdoer, as He, may He be Glorified, says:
{And if Allāh had willed, He could have taken vengeance upon them [Himself], but [He ordered armed struggle] to test some of you by means of others. And those who are killed in the cause of Allah - never will He waste their deeds.
He will guide them and amend their condition
And admit them to Paradise, which He has made known to them} [Muhammad 47:4-6].
And He, may He be Glorified, says:
{And if Allah had willed, they would not have fought each other, but Allah does what He wills} [Al-Baqarah 2:253].
And He, may He be Exalted, tells us that He may leave the transgressor alone, give respite to the wrongdoer and let the disbeliever get carried away, so that his sin and his punishment in this world and the hereafter may increase, as He says:
{But those who deny Our signs - We will progressively lead them [to destruction] from where they do not know.
And I will give them time. Indeed, My plan is firm} [Al-A`raf 7:182-183].
And He says:
{And thus is the punishment of your Lord when He punishes the cities while they are committing wrong. Indeed, His punishment is painful and severe} [Hud 11:102].
The point is that the existence of conflict, discord, injustice, aggression, killing, and corruption is part of the trial and test; it is also evidence of the existence, might, and power of Allah, may He be Exalted. For you see that Allah may grant respite to an oppressive nation, then He seizes them with the vehement grip of One Who is Almighty, Omnipotent, destroying them through means that are beyond human capability, such as unleashing winds, rains, floods, and the like, just as He did with `Ad and Thamud, and with Pharaoh.
Allah, may He be Exalted, says:
{Have you not considered how your Lord dealt with ʿAd –
[With] Iram – who had lofty pillars,
The likes of whom had never been created in the land?
And [with] Thamūd, who carved out the rocks in the valley?
And [with] Pharaoh, owner of the stakes?
[All of] whom transressed within the lands
And increased therein the corruption.
So your Lord poured upon them a scourge of punishment.
Indeed, your Lord is ever vigilant} [Al-Fajr 89:6-14].
You see the weak believing group, who are fewer in number and less well equipped, then Allah grants them victory when He wills, so they defeat their enemy and inherit his land and wealth, so everyone realises that victory is from Allah, and that all power is in the hand of Allah.
Allah says:
{And We wanted to confer favour upon those who were oppressed in the land and make them leaders and make them inheritors
And establish them in the land and show Pharaoh and [his minister] Haman and their soldiers through them that which they had feared} [Al-Qasas 28:5-6].
And He, may He be Glorified, says:
{[They continued] until, when the messengers despaired and were certain that they had been denied, there came to them Our victory, and whoever We willed was saved. And Our punishment cannot be repelled from the people who are criminals} [Yusuf 12:110].
And He, may He be Glorified, says:
{How many a small company has overcome a large company by permission of Allah. And Allah is with the patient} [Al-Baqarah 2:249].
Moreover, this dynamic of conflict and mutual injustice falls within the scope of the will and freedom of choice that Allah has granted to humanity; through this, people either wrong one another or show one another mercy. Had He made them a single nation, He would have stripped them of that freedom of choice.
The fact that humans have free will and the ability to choose is the basis of justice, ensuring they will be held accountable for their actions.
If most people were asked whether they would prefer to live this life compelled and coerced, possessing neither free will nor the ability to choose, or would they prefer to live as free agents possessing free will and the ability to choose, they would undoubtedly choose the latter.
As that is the case, it is astonishing that anyone would want humanity to be one nation, yet cite their differences and conflicts – which are the outcome of their free will and ability to choose – as grounds to question the existence of God.
III.
Debating with atheists and others who present specious arguments should be left to people who possess deep knowledge, because there is no guarantee that one who is ignorant or has little knowledge will not be led astray, because hearts are weak and the specious argument could mislead the one whose knowledge is lacking and the counter-argument presented by one who has little knowledge could increase the misguided person in misguidance and transgression.
Therefore this atheist should be directed to someone who is specialised in this field and can listen to his specious argument, debate with him and show him the right way. He should also be advised to look at websites that specialise in that.
What you mentioned about the specious arguments that impacted you is indicative of the danger of making friends with disbelievers and atheists, becoming fond of them and taking them as close friends rather than believers. Think about what sort of trouble you are putting yourself through because of that.
Allah, may He be Exalted, says:
{O you who have believed, do not take as intimates those other than yourselves [i.e., believers], for they will not spare you [any] ruin. They wish you would have hardship. Hatred has already appeared from their mouths, and what their hearts conceal is greater. We have certainly made clear to you the signs, if you will use reason.
Here you are loving them, but they are not loving you, while you believe in the Scripture - all of it. And when they meet you, they say: We believe. But when they are alone, they bite their fingertips at you in rage. Say: Die in your rage. Allah knows well what is in [your] hearts.
If good touches you, it distresses them; but if harm strikes you, they rejoice at it. And if you are patient and fear Allah, their plot will not harm you at all. Indeed, Allah has full knowledge of all that they do} [Al `Imran 3:118-120].
And He, may He be Exalted, says:
{O you who have believed, do not take My enemies and your enemies as allies, extending to them affection while they have disbelieved in what came to you of the truth, having driven out the Prophet and yourselves [only] because you believe in Allah, your Lord. If you have come out for jihad [i.e., fighting or striving] in My cause and seeking My pleasure, [take them not as friends]. How can you offer them friendship in secret when I know full well all that you conceal and all that you disclose? Whoever among you does that has indeed strayed from the right path} [Al-Mumtahanah 60:1].
See also the answer to question no. 23325.
And Allah knows best.
