Short answer
Both do. Anyone who makes a claim about reality has to give reasons for it, and "there is no God" is such a claim. Not being persuaded is a different thing. It is a report on one's own mind and claims nothing about the world. Every answer to why anything exists is a claim. It has always been, or it simply is, or it came from nothing, or a Creator made it. Each has to be weighed against the others. The 18th-century philosopher David Hume gave the rule: a wise man proportions his belief to the evidence. Islam adds that people are born with a natural leaning to know and worship their one Maker. Upbringing can cover it over, and this is a teaching about human nature, not a charge against anyone.
Full explanation
Whoever claims something about the world owes reasons
A burden of proof, the duty to back a claim with reasons, falls on anyone who says how things are. That includes the believer who says there is a Creator. It also includes the person who says there is none, or that the universe needs no cause. Only 'I do not know' and 'I am not yet persuaded' assert nothing. They are honest places to start from. David Hume gave a rule that fits every reader: a wise man proportions his belief to the evidence. This page applies that rule to the believer and the unbeliever alike. It does not claim that Hume reached the same conclusion. In the same essay Hume applied the rule to reports of miracles, Islam's included. Islam's main sign is not a report but a book anyone can examine today. The page on the Qur'an's challenge sets this out.
“A wise man, therefore, proportions his belief to the evidence.”
A lack of belief is not a view about the world
To lack a belief is a state of mind. A newborn child lacks belief in God (﷾), and so does anyone who has never met the question. A state a newborn can share settles nothing about the world. In 1972 the British philosopher Antony Flew proposed that atheist should mean simply "not a theist", that is, not a believer in God (﷾). He also proposed that a debate should start with the burden on the believer. His own terms keep a second kind apart: the positive atheist, who asserts that there is no God. Whoever says the arguments for God (﷾) fail has taken a position, and owes reasons for it.
Proposes that a debate about God should begin from a presumption of atheism, with the burden of proof on the theist. Reads "atheist" as "not a theist" (the negative atheist), and names the person who asserts that there is no God the positive atheist.
“A wise man, therefore, proportions his belief to the evidence.”
A starting rule is not a finding
A presumption is a rule for opening a trial. A court presumes innocence because a wrongful conviction costs so much. Flew's presumption is a rule for where a debate starts: do not believe until reasons are given. It is not a finding that there is no Creator. Like the presumption of innocence, it gives way once the evidence comes in. The evidence for a Maker is set out openly on three pages. They ask how we know God (﷾) exists, who created God (﷾), and why there is something rather than nothing.
Proposes that a debate about God should begin from a presumption of atheism, with the burden of proof on the theist. Reads "atheist" as "not a theist" (the negative atheist), and names the person who asserts that there is no God the positive atheist.
Argues that the sufficient reason for the whole series of contingent things must lie outside that series, in a necessary substance, which Leibniz calls God.
Every answer to why anything exists is a claim
Take the question why there is a universe at all. One answer is that it has always existed. A second is that it simply is, with no explanation. A third is that it came from nothing. A fourth is that a Creator who depends on nothing made it. Each answer says something about reality as a whole that no one has observed. Each is a claim and each has to be weighed against the rest. Some thinkers answer: 'we cannot know'. That is the agnostic's place, and it has its own path on this site.
Argues that physics can describe how a universe could arise from "nothing" without a creator. He uses "nothing" first for empty space, then for no space or time at all. He suggests that even the laws of physics may differ from one universe to another.
Argues that the sufficient reason for the whole series of contingent things must lie outside that series, in a necessary substance, which Leibniz calls God.
Divides all that exists into what is only possible in itself (mumkin al-wujud), which needs a cause, and what is necessary in itself (wajib al-wujud), which needs none. Argues that a chain of possible things, however long, needs a necessary being outside it, and that this being is one and has no parts.
What the saying and the teapot show
Two pictures are used to put the whole burden on the believer. The American astronomer Carl Sagan said that extraordinary claims need extraordinary evidence. That is fair as far as it goes. But it does not say which answer to the question above is the ordinary one. Each answer says something we have not seen about the whole of reality. Evidence has to choose between them. The British philosopher Bertrand Russell pictured a china teapot going round the sun, too small to see. Russell said no one could disprove it. Yet it would be nonsense, he said, to claim that doubters must therefore believe it. That is true of a made-up object. A teapot is a thing inside the universe. No argument leads to it, and it explains nothing. God (﷾) is put forward as the reason there is a universe at all, on arguments any reader can examine.
Popularises the saying that extraordinary claims require extraordinary evidence, in the episode on Encyclopaedia Galactica. It adapts Marcello Truzzi's "An extraordinary claim requires extraordinary proof" (Zetetic Scholar, 1978).
Says it is the business of those who hold a dogma to prove it, not of sceptics to disprove it. Pictures a china teapot circling the sun between Earth and Mars, too small to see: no one could disprove it, and it would be nonsense to say doubters must therefore believe it.
Argues that the sufficient reason for the whole series of contingent things must lie outside that series, in a necessary substance, which Leibniz calls God.
Islam's answer: bring your proof, and do not follow what you do not know
The Qur'an treats a claim as something to be argued. After asking who originates creation and who gives sustenance, it tells anyone who claims other gods besides Allah (﷾) to bring an argument (27:64). It tells the believer not to follow what he has no knowledge of (17:36). It also asks whether people were made from nothing, made themselves, or made the heavens and the earth (52:35-36). Those questions were put to people who denied the Prophet (ﷺ) in Mecca. Islam does not ask to be believed without reasons, and it gives them. The page on whether the Qur'an asks for blind faith takes up the verses about the unseen.
“Or, Who originates creation, then repeats it, and who gives you sustenance from heaven and earth? (Can there be another) god besides Allah? Say, "Bring forth your argument, if ye are telling the truth!"”
“And pursue not that of which thou hast no knowledge; for every act of hearing, or of seeing or of (feeling in) the heart will be enquired into (on the Day of Reckoning).”
“Were they created of nothing, or were they themselves the creators? Or did they create the heavens and the earth? Nay, they have no firm belief.”
Islam's answer: people are born with a leaning to know their Maker
Islam teaches that people are made with an inborn leaning to know and worship their one Maker, called the fitra (the natural disposition). It teaches that upbringing and habit can cover the fitra over, but not remove it. This is a teaching about human nature. It does not say that anyone who doubts secretly believes. The Prophet (ﷺ) said every child is born on the fitra. It is his parents who make him a Jew, a Christian or a Magian, which means a Zoroastrian (Bukhari 1385). That does not say a newborn holds beliefs. The Qur'an says people come from the womb knowing nothing (16:78). The fitra is a leaning, not a creed. Verses 30:30 and 7:172 are Islam's explanation of this sense, not evidence that it exists. The reader can ask himself whether he finds it, and the reasons above stand without it. A natural starting point does not excuse anyone from giving reasons once it is questioned. For Islam this knowledge of the Maker is the first step of a whole way of life, with worship and character following from it.
“So set thou thy face steadily and truly to the Faith: (establish) Allah's handiwork according to the pattern on which He has made mankind: no change (let there be) in the work (wrought) by Allah: that is the standard Religion: but most among mankind understand not.”
“When thy Lord drew forth from the Children of Adam - from their loins - their descendants, and made them testify concerning themselves, (saying): "Am I not your Lord (who cherishes and sustains you)?"- They said: "Yea! We do testify!" (This), lest ye should say on the Day of Judgment: "Of this we were never mindful": Or lest ye should say: "Our fathers before us may have taken false gods, but we are (their) descendants after them: wilt Thou then destroy us because of the deeds of men who were futile?"”
Abu Hurayra reports that the Prophet (ﷺ) said every child is born upon the fitra, the true faith, and it is his parents who make him a Jew, a Christian or a Magian, just as an animal gives birth to a whole young one: do you see any of them born mutilated?
“It is He Who brought you forth from the wombs of your mothers when ye knew nothing; and He gave you hearing and sight and intelligence and affections: that ye may give thanks (to Allah).”
The replies answered
Oppy, "Ultimate Naturalistic Causal Explanation" (2013)
Argues that where theism and naturalism fit the data equally well, naturalism is the simpler theory. Theism is committed to two kinds of thing, relation and cause, the natural and the supernatural; naturalism to one kind of each.
Cited for
Every view stops somewhere. Mine stops at the universe, which we know exists, so mine is simpler and needs no further proof.
The response
Simplicity is a tie-breaker between accounts that explain equally well. On the argument from dependence, a universe made of parts depends on those parts and on why it is this way. So it cannot be the thing that depends on nothing. The page on why there is something rather than nothing sets this out under the heading "The universe is not the necessary being".
Where it lands — Stopping at the universe leaves its dependence unexplained, so it is not the simpler complete answer.
Qur'an 52:35-36 — Surat al-Tur (The Mount), verses 35-36
“Were they created of nothing, or were they themselves the creators? Or did they create the heavens and the earth? Nay, they have no firm belief.”
Cited for
The Qur'an's questions leave out the option that the universe has always existed.
The response
The verses are questions put to people who denied the Prophet (ﷺ), not a full survey. This page names the eternal universe as one answer to be weighed. The argument from dependence reaches it too: whatever depends on other things needs, in the end, something that depends on nothing. Explaining each link by the one before it never explains why there is a chain at all rather than none. The German philosopher Leibniz (1646-1716) made this point: the reason for the whole series must lie outside it.
Where it lands — An eternal universe is weighed with the other answers, and the reasons from dependence apply to it as they do to the rest.
Sahih al-Bukhari 1385 — Kitab al-Jana'iz (Funerals), hadith 1385
Abu Hurayra reports that the Prophet (ﷺ) said every child is born upon the fitra, the true faith, and it is his parents who make him a Jew, a Christian or a Magian, just as an animal gives birth to a whole young one: do you see any of them born mutilated?
Cited for
A newborn holds no beliefs, so the saying that every child is born on the fitra cannot be true.
The response
The saying speaks of an inborn leaning, not of a belief held. The Qur'an itself says people leave the womb knowing nothing (16:78) and are then given hearing, sight and a mind. The leaning is what the Prophet (ﷺ) said parents can shape.
Where it lands — Islam says a baby has a leaning and not a creed, so the infant's lack of belief fits the teaching.
Qur'an 7:172-173 — Surat al-A'raf (The Heights), verses 172-173
“When thy Lord drew forth from the Children of Adam - from their loins - their descendants, and made them testify concerning themselves, (saying): "Am I not your Lord (who cherishes and sustains you)?"- They said: "Yea! We do testify!" (This), lest ye should say on the Day of Judgment: "Of this we were never mindful": Or lest ye should say: "Our fathers before us may have taken false gods, but we are (their) descendants after them: wilt Thou then destroy us because of the deeds of men who were futile?"”
Cited for
I remember no covenant, and no one can show that it took place. An inborn sense of God is an assertion with nothing behind it.
The response
This page does not offer 7:172 as evidence. It is Islam's explanation of the sense, given to believers. The case here rests on reasons any reader can weigh, and none of them needs the sense to be present.
Where it lands — The verse is Islam's explanation and not the proof, so a reader who recalls nothing loses nothing the argument needs.
Perspectives
Atheist and agnostic: the burden lies with the believer
Whoever says that something exists must show it. Believers say that God exists. Not being persuaded is the neutral starting point, just as a court begins by presuming a person innocent. And extraordinary claims need extraordinary evidence.
Atheism is only a lack of belief in God, so there is nothing for the atheist to prove.
Rebuttal
Flew's own terms split this. A negative atheist is simply not a theist and claims nothing. A positive atheist asserts there is no God, and anyone who says the arguments fail owes reasons.
The one who asserts must prove it. Believers assert God, so the burden starts with them, as a court starts by presuming innocence.
Rebuttal
Believers do owe reasons, and the reasons are on the table. But 'there is no Creator' is also a claim. A starting rule is a procedure, and evidence overturns it.
Extraordinary claims require extraordinary evidence, and belief in God is an extraordinary claim.
Rebuttal
Every account of why anything exists says something we have not seen about reality as a whole. The saying does not choose between them. Evidence has to. And Hume's rule applies to all of them.
A claim that cannot be disproved is not therefore to be believed. Russell's teapot shows that the burden lies on the one who asserts.
Rebuttal
That is true of an invented object. The teapot sits inside the universe, no argument leads to it, and it explains nothing. God (﷾) is offered as the reason a universe exists, on arguments open to test.
A universe can arise from nothing by physical law, so no Creator is needed.
Rebuttal
The philosopher of physics David Albert answered that the "empty space" of quantum physics is made of physical fields, so it is not nothing. He also asked where the laws of quantum physics come from. The view tells how a universe could arise. It does not tell why there are such fields and laws at all.
Every view must stop explaining somewhere. If some things may exist without a cause, the universe may be one of them, and that adds nothing we do not already know exists.
Rebuttal
Simplicity chooses only between accounts that explain the same things. On the argument from dependence, a universe with parts depends on those parts, and could have been otherwise. So it is not where explanation stops.
The burden is shared, so the evidence must decide
Whoever claims something about reality, for or against a Creator, owes reasons for it. Not being persuaded claims nothing and is an honest place to start from. Hume's rule applies to every reader.
Whoever makes a claim about reality, for or against God, owes reasons for it. And a wise person matches his belief to the evidence.
A mere lack of belief is a state of mind, not a position about the world.
There are several answers to why anything exists. The universe always existed. It is simply there, with no reason. It came from nothing. Or a Creator made it. Each of these is a claim that has to be weighed.
Sagan's saying and Russell's teapot do not move the whole burden onto the believer.
The Islamic perspective
Islam asks for proof from every claimant and gives its own reasons. It teaches that people are born with a natural leaning to know their one Maker, which upbringing can cover over.
The Qur'an tells anyone who claims other gods besides Allah (﷾) to bring an argument.
The Qur'an tells the believer not to follow what he has no knowledge of.
The Qur'an asks whether people were made from nothing, made themselves, or made the heavens and the earth.
Islam teaches that every person is born with a natural leaning to know the one Maker. This is the fitra, and upbringing can cover it over.
The Qur'an says people come from the womb knowing nothing. So the fitra is a leaning, not a set of beliefs that a baby holds.
Islam explains this sense through the verse of the covenant, when the children of Adam bore witness to their Lord. But the case on this page does not rest on it.