God & Cosmology: Perceptions & Opinions

[Chalnoth]

I'm not an expert on spontaneous symmetry breaking, but for the purposes of the (strong) anthropic principle you would really need enough trials (different sets of laws) that a life supporting universe becomes inevitable, or at least probable. Are you saying that this is supported by scientific evidence?

Well, we do exist, don't we? Whatever the true theory underlying the universe actually is, it must result in our existence. If a candidate for a theory of everything doesn't predict our existence, then it's wrong.

The weak anthropic principle, on the other hand, basically states that the universe supports life "because it does".

It states nothing of the sort. It just states that if we have a theory which predicts a variety of possible universes, only those parts in which observers can exist will be observed. It's a selection effect, in other words.

If you assume there's nothing special about life then there's nothing to be explained.

That's a statement that should not be simply assumed, but investigated in detail. And it doesn't appear to be true: from what we know currently, it does appear that a large number of parameters have to take a rather narrow range of values for life to be remotely possible.

 

[madness]

Well, we do exist, don't we? Whatever the true theory underlying the universe actually is, it must result in our existence. If a candidate for a theory of everything doesn't predict our existence, then it's wrong.

You have just reapplied the anthropic principle and ignored my point. If we assume life to be something unlikely and special we either need a designer or enough different trials that it would happen eventually. Neither one of multiple sets of laws or a designer is predicted. I could equally say that if the TOE doesn't predict a designer then it's wrong.

It states nothing of the sort. It just states that if we have a theory which predicts a variety of possible universes, only those parts in which observers can exist will be observed. It's a selection effect, in other words.

That's the strong anthropic principle - you are again assuming there are multiple universes. The weak anthropic principle simply states that if it was otherwise we wouldn't exist, ie if things were different, then they would be different.

That's a statement that should not be simply assumed, but investigated in detail. And it doesn't appear to be true: from what we know currently, it does appear that a large number of parameters have to take a rather narrow range of values for life to be remotely possible.

You misunderstood my point. If life is nothing special then that narrow range of parameters is no more interesting than any other range of parameters.

 

[Chalnoth]

You have just reapplied the anthropic principle and ignored my point. If we assume life to be something unlikely and special we either need a designer or enough different trials that it would happen eventually. Neither one of multiple sets of laws or a designer is predicted. I could equally say that if the TOE doesn't predict a designer then it's wrong.

Well, no, a designer is a non-starter, for the reasons I laid out previously, so we need a large number of trials if the conditions for life are unlikely.

A large number of trials with different physical parameters is an expected consequence of inflation + high energy physics.

That's the strong anthropic principle - you are again assuming there are multiple universes. The weak anthropic principle simply states that if it was otherwise we wouldn't exist, ie if things were different, then they would be different.

Yeah, I don't think you read what I wrote. Please try again.

You misunderstood my point. If life is nothing special then that narrow range of parameters is no more interesting than any other range of parameters.

What? That makes no sense. Nobody is suggesting that this narrow range of parameters is somehow "special", only that even if other ranges of the parameter space exist, it would be impossible for anybody to observe them.

 

[atyy]

For a classification of evidence to lead to the truth, that classification must lead to reliable results. That is to say, any sufficiently-specific statement about reality that you might make must be either true or false (another way of stating this is that it is possible to add conditions to any ambiguous statement so that it is definitively either true or false, even if we don't know which). This is basically a tautology.

Given this tautology, we can then conclude that if we are to accept a classification of evidence as being reliable, then it must consistently produce the same answers to the same questions. If it does not, then it is a bad form of evidence.

This fact is, fundamentally, why science relies so heavily upon verification of results. And it's also why there isn't any evidence for any god: the types of evidence that people attempt to use to support their beliefs are the same (revelation, personal experience, tradition), but they come to wildly different conclusions about the specifics.


He's using it in the way the word is used by the general populace, however. Now, I don't do this personally, but arguing over semantics doesn't get into the meat of the article. He is quite specific about the definition that he is using in the blog post.


I think it's typically only people that believe in a god that think that somehow the question, "Does a god exist?" is categorically different from other questions about the nature of reality. I don't. And that's what the thrust of that article was: it isn't categorically different, and so we should apply the exact same thought processes that have proven reliable time and again with other questions to the one about whether or not there is a god (or gods, for that matter).

See, I once believed in the Christian God. Then, as I learned about science and how to do science, I started applying those same thought processes to my religion (in particular after I noticed that my religion was making some claims that were distinctly opposed to reality). When I did so, I found that it was all bunk, and I really had no valid reason to believe any of it.


It's only perfectly fine if you're okay with being wrong. The only limitation placed upon scientific thinking is whether or not it is fallacious. Therefore there are only two types of reasoning: scientific reasoning (i.e. non-fallacious reasoning) and fallacious reasoning.


I find this human obsession with gods to be rather interesting. But seriously, if you're not going to demonstrate the existence of a god through rational means, then that's extremely good reason not to believe in a god.

Can you prove that one should use rational thought?

Can you prove that the world was not created one second ago with everyone's memory intact as it is to give the appearance of being created a long time ago?

 

[Phyisab****]

That's a misuse of the word "know". If you can't demonstrate it, you don't know. You may believe very strongly, but all the belief in the world doesn't make something true.

Fine, but you're just arguing over semantics. You just refuted the difference above. Anyways that doesn't change the point of my post.

 

[Chalnoth]

Can you prove that one should use rational thought?

As I said, you don't have to if you don't mind being wrong.

Can you prove that the world was not created one second ago with everyone's memory intact as it is to give the appearance of being created a long time ago?

Prove? No. But if we do a quick experiment and show that it conforms to expectations based upon past experience (past meaning before this hypothetical creation event), then we have shown that it is obscenely unlikely that the universe was created at that time.

 

[GeorgCantor]

Prove? No. But if we do a quick experiment and show that it conforms to expectations based upon past experience (past meaning before this hypothetical creation event), then we have shown that it is obscenely unlikely that the universe was created at that time.

It was obscenely unkely that the world would turn to not be flat, then that the Sun is not rotating around the Earth as it seems, then it was thought obscenely unlikely that the our universe would consist of relative objects in relative space and time. It was also thought that locality would hold no matter what. It was thought that realism would hold no matter what. We've seen this approach of things being "obscenely unlikely" take the wrong turn too many times. You can't rule something out just because it looks unlikely to you or somebody else.

 

[Chalnoth]

You can't rule something out just because it looks unlikely to you or somebody else.

It doesn't just look unlikely, though. It actually is. Here's the basic argument:
1. Consider the ensemble of all possible worlds that might have formed with people that have memories of a false past.
2. Because those memories are not rooted in actual experience, the memories will be unrelated to the nature of the latter world.
3. The vast vast majority of such worlds, therefore, will prove to be completely inconsistent with peoples' memories.
4. If our experiences accord with our memories, then, the past is likely real.

You can sort of get around this by supposing a deceptive designer, but that's a self-defeating hypothesis.

 

[madness]

Yeah, I don't think you read what I wrote. Please try again.

Maybe you didn't read what you wrote - "if we have a theory which predicts a variety of possible universes, only those parts in which observers can exist will be observed. It's a selection effect, in other words.". This is clearly the strong anthropic principle. You clearly assumed the existence of a variety of universes where observers can't exist.

What? That makes no sense. Nobody is suggesting that this narrow range of parameters is somehow "special", only that even if other ranges of the parameter space exist, it would be impossible for anybody to observe them.

This is the weak anthropic principle as I stated. The weak anthropic principle assumes life is nothing special and therefore doesn't need an explanation. The strong anthropic principle assumes multiple universes. And no you haven't shown multiple universes to be any more scientific than design.

 

[Chalnoth]

Maybe you didn't read what you wrote - "if we have a theory which predicts a variety of possible universes, only those parts in which observers can exist will be observed. It's a selection effect, in other words.". This is clearly the strong anthropic principle. You clearly assumed the existence of a variety of universes where observers can't exist.

I think you misunderstood the word "if" in that sentence, and you also should look up what the strong anthropic principle means.

This is the weak anthropic principle as I stated. The weak anthropic principle assumes life is nothing special and therefore doesn't need an explanation. The strong anthropic principle assumes multiple universes. And no you haven't shown multiple universes to be any more scientific than design.

Ugh, no. Here:
http://www.merriam-webster.com/dictionary/anthropic principle

 

[madness]

It doesn't just look unlikely, though. It actually is. Here's the basic argument:
1. Consider the ensemble of all possible worlds that might have formed with people that have memories of a false past.
2. Because those memories are not rooted in actual experience, the memories will be unrelated to the nature of the latter world.
3. The vast vast majority of such worlds, therefore, will prove to be completely inconsistent with peoples' memories.
4. If our experiences accord with our memories, then, the past is likely real.

You can sort of get around this by supposing a deceptive designer, but that's a self-defeating hypothesis.

Do you realize the law of entropy is time symmetric? ie entropy should increase back in time just as much as forward. This means that it overwhelmingly more likely that the universe formed into stars and planets (and human brains) as a statistical fluctuation from disorder. This then means that all our memories are most likely imagined.
Don't worry, I'm not advocating this point of view, but it's interesting to think about. Of course, the argument undermines itself - if it is true, then our scientific reasoning on entropy is no longer valid. The solution is to assume the universe began with incredibly low entropy. This is incredibly unlikely statistically, but at least it doesn't undermine itself.

 

[madness]

I think you misunderstood the word "if" in that sentence, and you also should look up what the strong anthropic principle means.

"If" what you said isn't true, then there's no selection effort (which you said there was).


From wikipedia, 3 statements of the SAP:

"There exists one possible Universe 'designed' with the goal of generating and sustaining 'observers.'"

"Observers are necessary to bring the Universe into being."

"An ensemble of other different universes is necessary for the existence of our Universe."

The third is the one I was referring to. The other 2 are just as unscientific.

 

[Chalnoth]

Do you realize the law of entropy is time symmetric? ie entropy should increase back in time just as much as forward. This means that it overwhelmingly more likely that the universe formed into stars and planets (and human brains) as a statistical fluctuation from disorder. This then means that all our memories are most likely imagined.

This is precisely the situation I was talking about. It is trivially refuted by the reliability of past memories, because in the vast majority of such universes, past memories will be entirely unrelated to the nature of the world.

This problem is a well-known problem, and also well-known is where the solution must lie: in cosmology. Basically, the reason why we have a real past must be because there was a very low-entropy configuration in the distant past, and the laws of physics must be such that low-entropy configurations of that type are more likely than a simple thermodynamic argument would suggest.

 

[Chalnoth]

"If" what you said isn't true, then there's no selection effort (which you said there was).

The selection effect is there whether or not there are universes which don't have physical laws conducive to the formation of life.

From wikipedia, 3 statements of the SAP:

"There exists one possible Universe 'designed' with the goal of generating and sustaining 'observers.'"

"Observers are necessary to bring the Universe into being."

"An ensemble of other different universes is necessary for the existence of our Universe."

The third is the one I was referring to. The other 2 are just as unscientific.

Well, I really don't agree with Barrow and Tipler's third option there, and it's particularly telling that nobody else appears to make use of that one. But regardless, I never said that an ensemble of other different universes is necessary. I merely said that if the laws of physics are such that different regions will produce different low-energy laws of physics (which our current knowledge of high-energy physics appears to support), and if our universe is sufficiently large (which our current knowledge of inflation appears to support), then we are have a system with a large number of regions, many of which are unlikely to be habitable.

In other words, the evidence is very clearly and definitively pointing in the direction of just such a multiverse. And when evaluating any particular multiverse hypothesis, it is necessary to take into account the weak anthropic principle.

 

[madness]

Well I agree that the weak anthropic principle tells us that our observable universe is biased towards life. I don't agree that it sheds any light on why our universe supports life (although I'm not sure whether you are arguing that). I have no major problem with the strong anthropic principle on philosophical grounds, so long as it isn't couched as science.

 

[Chalnoth]

Well I agree that the weak anthropic principle tells us that our observable universe is biased towards life. I don't agree that it sheds any light on why our universe supports life (although I'm not sure whether you are arguing that).

All I'm saying is that you have to take the weak anthropic principle into account when considering prolific theories. A proper use of the principle, for example, would be the following: consider that we are comparing two theories, X and Y. These theories predict probability distributions for the parameter A. For theory X, all values of A are equally likely. For theory Y, larger values of A are obscenely more likely than smaller values (e.g. P(2A) = 10^6 P(A)).

Then we go out and measure this parameter A, and come up with an answer of 1.999. What does this mean? Well, to have any idea whatsoever, we have to take into account the weak anthropic principle: if we find that life is only possible if 1 < A < 2, then our measured value of this parameter A would seem to strongly support theory Y.

In other words, the weak anthropic principle isn't an explanation of anything. It's just something we need to consider when examining competing theories.

As to why our universe supports life, as opposed to some other, I would consider that a meaningless question in the first place.

 

[madness]

Doesn't this violate the Copernican principle? But yes I agree with your use of the weak anthropic principle. My problem is its use as a "scientific" alternative do design (not that design is any better).
The question isn't why our life supports life as opposed to some other, its why life (conscious beings) exist at all. Some people consider this a serious question, others might argue that the universe just happens to be that way.

 

[yoda jedi]

A pretty loaded title for the thread (I know).

I would like to know what are everyone's perceptions/opinions regarding the beginning of the universe (of time) as it relates to the notion of a god or God?

i think that this STATE come from a more primordial STATE (eternal), elements without time generate this STATE (by deviation) time is created and entropy run (this STATE).

god for ?

 

[Freeman Dyson]

People often have little problem holding two incompatible ideas within their own heads.

Who says that religion and science are incompatible?

 

[Chalnoth]

Doesn't this violate the Copernican principle?

I don't see how.

But yes I agree with your use of the weak anthropic principle. My problem is its use as a "scientific" alternative do design (not that design is any better).

Well, as I said earlier, design isn't even on the table. It's a complete non-starter. I don't think anybody seriously considers the anthropic principle in any way related to design. In serious circles, the only two alternatives considered are whether the specific low-energy physical laws can be uniquely predicted from a theory of everything, or whether the theory of everything is prolific. To me, a prolific theory of everything seems vastly more likely (not least because we already seem to see some evidence of spontaneous symmetry breaking).

The question isn't why our life supports life as opposed to some other, its why life (conscious beings) exist at all. Some people consider this a serious question, others might argue that the universe just happens to be that way.

Well, in a way it's a serious question, in that the fundamental laws of physics must necessarily predict that life is possible for those laws to be accurate (given the fact that we exist). But other than that it's basically meaningless.

 

[Freeman Dyson]

Well, no, a designer is a non-starter, for the reasons I laid out previously, so we need a large number of trials if the conditions for life are unlikely.

A large number of trials with different physical parameters is an expected consequence of inflation + high energy physics.Yeah, I don't think you read what I wrote. Please try again.What? That makes no sense. Nobody is suggesting that this narrow range of parameters is somehow "special", only that even if other ranges of the parameter space exist, it would be impossible for anybody to observe them.

You mean "expected" as like things String Theory "expects"? Anything observational backing this up?

From the wiki on inflation:

At present, however, whilst inflation is understood principally by its detailed predictions of the initial conditions for the hot early universe, the particle physics is largely ad hoc modelling.

and

One of the most severe challenges for inflation arises from the need for fine tuning in inflationary theories. In new inflation, the slow-roll conditions must be satisfied for inflation to occur. The slow-roll conditions say that the inflaton potential must be flat (compared to the large vacuum energy) and that the inflaton particles must have a small mass.[55] In order for the new inflation theory of Linde, Albrecht and Steinhardt to be successful, therefore, it seemed that the universe must have a scalar field with an especially flat potential and special initial conditions.

oh, and Susskind specifically refers to the parameters of our universe as "special". Penrose does the same. I'll show you videos if you don't believe me.

 

[Chalnoth]

Who says that religion and science are incompatible?

Pretty much everybody who has thought about it seriously. Religion relies upon divine revelation to determine what is true and false (e.g. many forms of Christianity rely upon the Bible, which is believed to be divinely inspired, to determine the truth or falsity of statements). Science relies upon rigorous investigation and skepticism. Those are two entirely incompatible ways of determining the truth or falsity of statements.

 

[madness]

Well, as I said earlier, design isn't even on the table. It's a complete non-starter. I don't think anybody seriously considers the anthropic principle in any way related to design. In serious circles, the only two alternatives considered are whether the specific low-energy physical laws can be uniquely predicted from a theory of everything, or whether the theory of everything is prolific. To me, a prolific theory of everything seems vastly more likely (not least because we already seem to see some evidence of spontaneous symmetry breaking).

Well, since evolution basically threw Pailey's teleological argument out the window, many people tried to shift the need for design to the universe as a whole. How can it be that the laws of physics are just right to allow atoms to form stars which in turn create the elements needed for biochemistry etc (their argument not mine). So people used the anthropic principle as a (scientific) counteragrument. My point was that the anthropic principle in its strong form is no more scientific than the argument for design, and in its weak form doesn't really address the problem. Of course, as I said before, you might argue that there's no problem to begin with.

 

[Chalnoth]

You mean "expected" as like things String Theory "expects"? Anything observational backing this up?

Even the standard model of particle physics includes spontaneous symmetry breaking. No need to go to speculative theories about physics beyond the standard model.

oh, and Susskind specifically refers to the parameters of our universe as "special". Penrose does the same. I'll show you videos if you don't believe me.

There are a number of facts about our universe that demand explanation, such as the incredibly small (but apparently non-zero) value of the cosmological constant. What that explanation is is still open, though I strongly suspect a prolific theory of everything, for a variety of reasons.

 

[Chalnoth]

How can it be that the laws of physics are just right to allow atoms to form stars which in turn create the elements needed for biochemistry etc (their argument not mine). So people used the anthropic principle as a (scientific) counteragrument.

Well, I'm not talking about what people use in the public sphere here. I'm talking about within the scientific community itself, where design isn't even considered because it's a pointless argument to begin with.

 

[madness]

I'm not talking about the public sphere either, I'm talking about philosophy, where the anthropic principle is most commonly debated.

 

[Freeman Dyson]

Pretty much everybody who has thought about it seriously. Religion relies upon divine revelation to determine what is true and false (e.g. many forms of Christianity rely upon the Bible, which is believed to be divinely inspired, to determine the truth or falsity of statements). Science relies upon rigorous investigation and skepticism. Those are two entirely incompatible ways of determining the truth or falsity of statements.

I love Chuck Berry. I like what John Lennon said about him. "If you tried to give rock and roll another name, you might call it 'Chuck Berry'." If you tried to give science another name, you might call it Francis Bacon. He comes into your post a lot here. First sentence,

Pretty much everybody who has thought about it seriously.

Bacon: "God forbid that we should give out a dream of our own imagination for a pattern of the world."

Which is what you are doing.

If truth relied only on divine intervention, then there would not be any religious scientists. Nor would deeply religious people like Bacon and Alhazen have laid the groundwork for the scientific method. Neither of us probably know anything about theology/comparative religion so I don't know what all these religions say is the only truth anyway. So that should be, as you say, a non-starter.

The only thing we can do is look at the actions of religious people, because without them, religion doesn't exist. Religion only lives through them. And religious people are a diverse bunch. Just look at American Christians. You got everybody from Ted Kennedy, Francis Collins, Pelosi, Obama, etc.. to Pat Robertson. How about the English? Jane Goodall is a Christian and sees purpose in the life she studies. Richard Dawkins is an atheist and doesn't see any purpose in the life he studies. It is a philosophical view of the world and has nothing to do with science, or hinder science, when done correctly.

 

[Lateralus.]

Pretty much everybody who has thought about it seriously. Religion relies upon divine revelation to determine what is true and false (e.g. many forms of Christianity rely upon the Bible, which is believed to be divinely inspired, to determine the truth or falsity of statements). Science relies upon rigorous investigation and skepticism. Those are two entirely incompatible ways of determining the truth or falsity of statements.

Wrong.

Atheism is a religion which does not rely on divine revelation.

 

[Evo]

Wrong.

Atheism is a religion which does not rely on divine revelation.

Wrong, atheism is not a religion.

 

[Lateralus.]

Wrong, atheism is not a religion.

How is it not?

 

[union68]

Regarding God and cosmology:

I am an agnostic that tends towards atheism but have found myself defending religion on more than one occasion. My issue with your prototypical, every-day atheist is not that I believe he/she is wrong, rather my issue is with their argument.

If the argument is ever pushed into the "origin of the universe," the atheist inevitably will cite the Big Bang or will use some other grand cosmological argument to prove the non-existence of God. They'll start talking about string theory, multiple universes, blah blah... The person is obviously a layman on such an issue and is simply parroting what he/she heard last week on the Discovery Channel.

Now, clearly, clearly, the atheist is accepting the truth of these cosmological arguments completely on faith. He/she has NO idea how physics arrived at those (speculative) theories and has never tinkered with a single equation. They are completely ignorant to all of science except, apparently, they can sweep away God by citing theoretical physics. They cannot believe that a man walked on water, but can believe that multiple universes exist. Ok... They both sound equally fanciful to me.

It would be a safe estimate to say that most people are laymen when it comes to these theories, but yet, if it is branded with "science," they will all accept it with almost no question. It seems that the popularizations of theoretical physics have just as much sway over these people as a preacher does with his/her congregation.

Now, please do not misunderstand my writing. The atheist I have mentioned is the average kid at the local coffee shop or bar that I've argued with before, not a trained scientist. Further, I am not trying to say that these theories are wrong or are nonsense, I am just pointing out that your average atheist is wielding arguments that they believe true only because somebody told them they were true, which -- ironically -- is exactly the kind of submissive mentality that they claim to hate.

I am not advocating strict empiricism. I'm not the guy who refuses to believe in atoms just because I can't see them myself. What I am advocating is a little bit of healthy skepticism.

Finally, I do not think it is science's job to either prove or disprove God, and I firmly believe that any scientist who actively tries is a deluded fool. If the theists say that there is a God, the burden of proof falls on them; hence, science should not waste its time with this "disproving God" drivel. While science can spur interesting problems in both philosophy and theology, neither philosophy nor theology belong in the natural sciences.

 

[DaveC426913]

How is it not?

Quite simply, an atheist does not hold any beliefs on faith.

You are thinking atheists say "I believe there is no God". They do not; they simply say "I do not believe there is a God". It's not the same thing.



As an aside, I wonder how many atheists would be delighted to be proven wrong...

[Personal speculation]
See I don't think atheists want there to not be a God. What they want is truth, whichever outcome it is. If God were proven to be true, that would actually be the best possible outcome for an atheist, since they can now know the answer to the God/no God mystery.

Note that it also means any given athiest is not a card-carrying atheist; they would immediately update their world view to match the facts. A rare case where being "fickle" is a virtue.

And that's why it's not a religion.
[/Personal speculation]

 

[Lateralus.]

Quite simply, an atheist does not hold any beliefs on faith.

You are thinking atheists say "I believe there is no God". They do not; they simply say "I do not believe there is a God". It's not the same thing.

http://dictionary.reference.com/browse/religion

re⋅li⋅gion  /rɪˈlɪdʒən/ Show Spelled Pronunciation [ri-lij-uhn] Show IPA
–noun 1. a set of beliefs concerning the cause, nature, and purpose of the universe, esp. when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
2. a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects: the Christian religion; the Buddhist religion.
3. the body of persons adhering to a particular set of beliefs and practices: a world council of religions.
4. the life or state of a monk, nun, etc.: to enter religion.
5. the practice of religious beliefs; ritual observance of faith.
6. something one believes in and follows devotedly; a point or matter of ethics or conscience: to make a religion of fighting prejudice.
7. religions, Archaic. religious rites.
8. Archaic. strict faithfulness; devotion: a religion to one's vow.


Would atheism not fall under the bolded descriptions? Or is the definition of 'religion' too broad?

 

[Gokul43201]

But without any evidence whatsoever, it makes the statement "a god exists" an unreasonable one to hold.

By the rules of physics yes. By the rules of theology no. There are religions which are based on the fundamental belief that there are truths in the universe which cannot be proved and must be accepted on faith, and faith alone, and that only by accepting certain statements without any evidence or rationale, can one be saved.

By your own construction (t-q), within the religions you speak of, the existence of a god (if that is one of the "truths" you refer to) is to be accepted on faith alone, and can not be deduced through reasoning. Ergo, it is unreasonable.

 

[Evo]

How is it not?

Oxford dictionary

www.askoxford.com

religion

• noun 1 the belief in and worship of a superhuman controlling power, especially a personal God or gods. 2 a particular system of faith and worship. 3 a pursuit or interest followed with devotion.

The best explanation I've seen for a theist to understand that an atheist simply doesn't care and doesn't believe is here.

The broader, and more common, understanding of atheism among atheists is quite simply "not believing in any gods." No claims or denials are made — an atheist is just a person who does not happen to be a theist. Sometimes this broader understanding is called "weak" or "implicit" atheism. Most good, complete dictionaries readily support this.

There also exists a narrower sort of atheism, sometimes called "strong" or "explicit" atheism. With this type, the atheist explicitly denies the existence of any gods — making a strong claim which will deserve support at some point. Some atheists do this and others may do this with regards to certain specific gods but not with others. Thus, a person may lack belief in one god, but deny the existence of another god.

Unfortunately, misunderstandings arise because many theists imagine that all atheists fit this most narrow, limited form of the concept of atheism. Reliance upon dishonest apologists and cheap dictionaries only exacerbates the problem. So, when someone identifies themselves as an atheist, all you can do is assume that they lack belief in the existence of any gods. You cannot assume that they deny any gods or some particular god — if you want to find out about that, you will have to ask.

Why do these errors occur? Why do some theists insist that the broader sense of atheism simply does not exist? Possibly some theists feel that since they are claiming the existence of their god, then anyone who does not agree with them must be claiming the exact opposite — a serious misunderstanding of not only basic logic but also how human belief systems operate.

continued...

http://atheism.about.com/od/definitionofatheism/a/whatisatheism.htm