This is not intended to be reasons why believers should give up their faith – heaven help us from evangelical atheists!
You do not need reasons not to believe, and even though nothing can completely disprove the existence of the supernatural, if someone’s non-belief is based on reasons it might be some of these or they may now consider that these reasons support their non-belief;
1: The weakness of the opposing arguments - the so-called proofs of God's existence.
Of course it is up to the individual to decide for themselves what constitutes convincing proof but most non-believers who have taken time to consider the proofs fall on the side of ‘lack of convincing evidence’ since clearly if you have found any of the arguments convincing you would not be an atheist.
The proofs of god commonly touted about do not rely on proof at all but faith in what you have been told by someone to be true, in other words ‘proof’ of god relies on unsubstantiated faith.
Should we expect a god to provide proof of its existence? Perhaps, because looking at Holy Scriptures gods are always popping up doing the impossible so their existence should be easily provable - but it isn't.
2: Common experience: If God existed, he should be easier to see or sense. People praying for advice on similar subjects should on the whole get similar answers.
If you look at issues that divides churches – women clergy, abortion, gay relationships/clergy. etc. You can find denominations that accept and reject all of these to varying degrees, from total intolerance to complete acceptance.
Perhaps I am wrong to assume that the leaders of these churches have asked their gods guidance on these matters, but they should have and if they did god should have told them basically the same thing. But what we have, assuming most religious ministers have studied their scriptures and prayed for guidence, is for example, that some will accept gays, even allowing them to preach, others will say they are going to hell for being gay etc. And all appear to believe they are following their faith correctly.
3: Refusal to explain something you cannot understand by something you understand even less.
Examples; “God is unknowable, god works in mysterious ways, no one knows the mind of god, gods plan is not revealed to us” etc. How many times have I heard these or similar sound bites? Yet the people saying them usually go on to tell everyone exactly what god wants and if we don’t understand something we are asked to accept it because god knows or god did it.
4: In all likelihood our consciousness does not survive death. People with even minor brain damage can change personalities and forget family and language. What's likely to happen when the whole brain dies?
Most believers think they will be much the same person, personality wise, in the after life, but somehow a mentality disabled person will be different. Unfortunately this idea occurred to me sometime ago when my best fried at the time had an accident and suffered a serious a serious brain injury. Even after his fullest recovery he was never the person I knew.
An after death ‘cure’ for all your mental flaws, and we all have them, would change who we are and seems all a bit of a theological fudge.
5: The mediocrity of mankind - that there is nothing special about humans or the Earth we are part of the biosphere, not above it or unique to it.
‘Speak for yourself!’ is usually a theist’s first reply to this. But this is a bit like saying I’m an individual, just like everyone else in the world! I feel it is arrogant to set myself above other life and every planet is unique. Man is not a special animal in any meaningful way.
I think is arrogant to believe otherwise as other animals are as equally evolved to their environments as we are. It is easy to point out how unique we are to other animals but it is just as easy to point out how unique they are to us.
Bertrand Russell said “Theology induces a dogmatic belief that we have knowledge where in fact we have ignorance, and by doing so generates a kind of impertinent insolence towards the universe.” I think he is right; it is insolent to think this universe was created with us in mind.
6: Lack of evidence for claims – none of the claims made by religions, (miracles, healing, effectiveness of prayer), stand up to scientific scrutiny.
Research has been done into all these including by religiously funded organisations, especially prayers for the sick. Although people with a strong positive outlook, whether gained through religious belief or not, often do a little better, nothing significant was found.
That really only leaves two choices;
1: The evidence proves that these things do not happen above the rate of probability or coincidence no matter how much people want to believe in them.
2: God refuses to reveal himself to those doing the research.
The first is most likely. No one would have any trouble accepting this kind of research if it was carried out on any other subject.
When it comes to the second, I have to ask myself; why would a god that is supposed to be loving let people suffer and die just to hide his presence from people who he wants to believe in him and worship him anyway?
An argument I have seen against this is that if everyone knew there was a god everyone would do the right thing out of fear, but lots of people really believe in gods and still go against them. A sin is only a sin if you believe there is a god to sin against. So it is perfectly reasonable for a god to give evidence of their existence and still leave us with free will.
7: Religion is Self-Contradictory.
Religions contradict themselves. Are there any beliefs in Christianity, Islam, Scientology, Hinduism etc. that are different even opposite from the other faiths?
All three mono-theistic religions evolved from the same source so they will have similarities and there is little to choose between their basic philosophies. However the religions they eventually replaced and others existing today are only similar in the broadest sense. The South American religions, Hinduism, Buddhism etc are very different and many of the similarities appear to be adopted from each other rather than having them arise separately as you would expect if driven by a common intelligence.
Even the different flavours of the same basic faith contradict each other including Christianity. Catholics believe in the trinity, priests as intermediaries for confession, the status of the virgin Mary etc. Protestants don’t. Add in all the other groups and sects and there is nothing but contradiction!
Because of this religious groups do not speak with one voice on any of many subjects, and even fight each other over the correct way to worship.
And this is a theist argument; My faith is different from all others (and the true one?), but this is also an argument for atheism. If most religions are wrong, and they must be, then why not them all?
8: Gods and Believers Behave Immorally.
There are plenty of examples of immoral behaviour amongst most gods and their faithful when that behaviour is compared to modern standards.
For example different interpretations of scripture are used to tell followers quite explicitly what is right and what is wrong - even when other interpretations and most of society disagree. They will swear on the Bible that they believe they are doing as commanded by their god – I have no reason to think them liars.
But all morality is relative. We do not accept things like Slavery, oppression of minorities, unequal rights, etc. They are wrong today even though many considered the acceptable in times past. All scripture I have come across, including the Bible, have dubious to down right immoral actions done by gods and their believers when compared to modern western standards.
Some religious people behave immorally, according to my moral standards and often those of other religious people as well, but they do it by believing they are doing what their god wants. So we have mistreatment of some sections of people and those who commit suicide attacks believing they will earn a place in heaven by doing it.
9: The Concept of God is Incoherent.
How is god described by different groups of believers and theistic individuals? Will a Muslim’s description be the same as a Hindu’s? What about a Mormon or pantheist?
It is true that all religions do not speak with a single voice on this. Jesus stated that he was the way the truth and the light, no one shall enter the kingdom of heaven but through him. Sects likes Mormons and Witnesses believe that they are the only ones on the right path. Other religions have similar sayings supporting there own doctrines as the true way. Again this just shows the contradictory and incoherent nature of gods and religions.
10: God corresponds so perfectly to our wishes that there is every reason to think he was invented to fulfil them, at least in fantasy; if accepted this would make religion an illusion or delusion.
Nobody wants death to be the End; religions usually claim to give us the chance of a betterworld and eternal life through theistic belief. This applies to many of our desires. We want a better life, not to get ill but recover from illness, be able to help others especially our family and friends, get good advice and consolation in times of despair. Belief in god usually offers all this.
Belief in gods fulfils these needs. People who feel that life is unjust want to believe that the bad people will get what they deserve and the good get rewarded in a way that they never did through their life. Religion fills this need. Hell is a bad place and heaven is a wonderful place. Whatever religious people make of the afterlife it usually fits perfectly with their wishes.
There may of course be many other reasons - not least annoying Christians!