What's the difference between agnosticism, theism and atheism? Before I did the research for this essay, I thought I knew the answers. Are these mutually exclusive worldviews? And if they aren't mutually exclusive, who is and who isn't agnostic? Why do agnostics lack knowledge about theological issues, and what should I tell my nieces and nephews when they ask me if god exists?
The first agnostic
Thomas Huxley coined the term "agnostic," which was designed to be "suggestively antithetic to the 'gnostic' of Church history..." He elaborated on his thinking in "Collected Essays" :
"When I reached intellectual maturity and began to ask myself whether I was an atheist, a theist, or a pantheist; a materialist or an idealist; a Christian or a freethinker; I found that the more I learned and reflected, the less ready was the answer; until at last, I came to the conclusion that I had neither art nor part with any of these denominations, except the last. The one thing in which most of these good people were agreed was the one thing in which I differed from them. They were quite sure they had attained a certain "gnosis," --had more or less successfully, solved the problem of existence; while I was quite sure I had not, and had a pretty strong conviction that the problem was insoluble."
To understand what Huxley means by agnostic, it is, in part, important to understand the history of the "gnostic" in the Church history to which he refers. Gnosis refers to spiritual or revealed knowledge of divine origin as compared with natural or material evidence. In the early days of Christianity, the "gnostics" preferred revealed knowledge to faith (pistis) in the teachings of other Christians.
Huxley patently rejects spiritual or revealed, personal knowledge as compared with epistemological knowledge. For Huxley, the implicit distinction is between warranted beliefs based on natural, independently-verifiable evidence and extreme beliefs that are baseless. Revealed knowledge is unwarranted, as it fails to produce natural evidence for itself and is subjective insofar as it varies by the person for which it is "true" since revealed "knowledge" can simultaneously infect different people and evoke irreconcilably different realities, given the wide range of irreconcilably different solutions that exist for the "problem of existence."
I think it is important to emphasize that Huxley is coining the term agnosticism as an antithesis to theism but also to atheism and many others, which according to Huxley require a host of unwarranted beliefs in their own right. The sin in Huxley's religion is to be passionately wedded to any "-ism" without good evidence. In this sense, perhaps a better name for the term would have been apisticism (using the Greek root pistis for "faith" or "belief") instead of agnosticism. For better or worse, agnosticism stuck.
The tracking theory of knowledge
Since Huxley wrote in the 19th century, a revolution occurred in the field of epistemology, the philosophical study of knowledge, when, in the late 20th century, Robert Nozick proposed his highly influential "tracking theory" of knowledge . I like to think that Huxley would have immediately embraced the theory. According to the theory, which I have only mildly adapted here, to know a proposition, P, by some method, S, the following four criteria must be true about you and your method:
1) P is true
2) you believe P (according to method S)
3) if it weren't true that P, you wouldn't believe P (according to S)
4) if it were true that P, you would believe P (according to S)
With this simple theory, Nozick described the relationship between, truth, knowledge and belief, something no one before him was adequately able to accomplish!
Let's quickly run through an example of how I can know that my name is Harvey by the tracking theory of knowledge. If you already understand this theory, please just skip ahead to the next section, if you don't, please read this - it is one of the coolest things I learned in undergrad.
1. Is P true? It is true that my name is Harvey, so I pass the first criterion.
2. Do I believe P? I believe that my name is Harvey (according to my method of trusting that my family has been honest with me about my name since early childhood), so I pass the second criterion.
The first half, as usual, was pretty straightforward; now for the counterfactuals. For the third and fourth criteria, we are asked to consider alternate universes that are similar to our own but different in important ways. These final criteria test the tracking strength of our method. If the method is robust enough and the criteria are still met, we can say that we know P to the extent that our method survived the counterfactuals we chose.
3. If P weren't true, would I not believe P? If my name weren't Harvey, it would be some other name like Stewart (that is what my mom tells me anyway, I just asked her and I am happier than ever with Harvey). Therefore, I wouldn't believe my name was Harvey (according to my method, I would believe my name is Stewart), so I would pass the third criterion.
4. If P were true, would I believe P? If my name were Harvey but my family called me by my middle name, I would still believe my name was Harvey since they would have divulged my full name at some point (for my admission to school for example). Therefore, I would continue to believe that my name was Harvey and pass the final criterion.
Note: My family still calls me by my middle name, so the second counterfactual wasn't difficult to imagine at all.
Since all the criteria are met, we can say that I know my name is Harvey to the extent that my method is robust to the challenges raised in the third and fourth criteria. This does not mean I have absolute certainty, since my method might not have been strong enough to best challenges like being switched at birth in a bizarre hospital mix up or having an unknown error on my birth certificate. Finally, I want to make clear that an explicit method is not required for his theory. Any implicit method in our neurological make-up could be sufficient to know things (e.g. that I am hungry as I type).
With his theory, the late Robert Nozick has provided us with the tool we need to compare the belief systems of theists, atheists and agnostics.
Agnostics, atheists and theists share a lack of knowledge
We can now use the tracking theory of knowledge to compare the knowledge status of theistic and atheistic belief about god. Would Nozick say they have knowledge or not? What do you think? The following propositions, P, and methods, S, will be used respectively for the theists and atheists:
P: "God does exist"
S: "Unquestioning faith in god"
P: "God does not exist"
S: "The (dearth of) evidence for god"
1. Are the P's true? I think it is fair to say that there is no proof of god's existence or non-existence and we can take the truth of P to be functionally unknowable. Either way, let's suspend any knowledge judgement overall until we see the rest of the criteria.
2. Do they believe the P's? This is a no-brainer. This will hold for both parties.
As expected, for criteria three and four, things get more interesting.
3. If the P's weren't true, would they not believe the P's? The important thing to recognize is that the method of belief is critical for the outcome of this thought experiment. I will assume that the theist and atheist practices what I deem to be the most popular forms of theistic and atheistic belief. For the theist, if the method of belief is unquestioning faith in a god, who is testing humanity's resolve (as is presented as the model for Jews, Christians and Muslims in the story of Job), the theist is going to fail this counterfactual every time since under no circumstance would the theist not believe in god.
For the atheist, if the method of belief is evidence in the existence of god, it is at least possible to imagine the atheist occasionally passing this criterion, but it is highly unlikely since skepticism can be just as deeply seated as religious belief. We might imagine that by god we mean a being with superhuman intelligence with the power to perform miracles, etc. and a skeptical atheist could be theoretically convinced that a "god" did exist if such a being materialized before the atheist and revealed the evidence. However, if the atheist doubted the performance as being magical or a dream, etc., etc., or the being did not perform for the atheist because it had better things to do with its time, the atheist would fail this criterion, and such a god would not be faulted for failing to want to spend much time with its critics.
Further, I should mention that I suspect a lot of atheists would fail this counterfactual because their atheism is a reactionary atheism to straw man gods from holy texts (filled with, for example, stories of the creation of man compared with the more parsimonious, in my opinion, evolutionary theory) that they would likely not even recognize a real god or maybe mistake it for an alien, given their propensity to expect, if anything, a recognizable anthropomorphic god and given their well-practiced and rewarded skepticism.
4. If the P's were true, would they believe the P's? Here, the "Job-theists" have no problem meeting this criterion. They will always believe in god, no matter what. The atheist using evidence based methods would probably do fairly well convincing himself or herself of his belief based on evidence alone.
So while the story has some texture, we have come to the conclusion that many of you probably expected. Theists do not know that god does exist, nor do atheists know that god does not exist according to the tracking theory of knowledge by failing to pass criterion three.
As you thought about criterion one, you might have wondered if it is possible to know without knowing that you know, and indeed this is a possibility. Under situations where all the conditions are met, but you don't know that they have been, then you may know without knowing that you know. This means that you have knowledge without certainty since certainty is a property of knowing that one knows.
A consequence of the above analysis of theists and atheists is that they are technically agnostic, in that they lack knowledge. Theists of the revealed knowledge ilk, such as the early Christian gnostics, perhaps, would argue that the right sort of theists were not tested, but I do not believe that this group is very representative of theists, in general, except for the rare fundamentalist. Most of the theists I speak with are quite proud to be faithful in the face of a complete absence of evidence. However, if I had included this group, I would have argued (successfully, I think) that they fail the third criterion as well.
In case you were wondering, agnostics fail the knowledge test at the earliest possible point. They don't even choose a proposition, P. This is equivalent to the Un-mode of Zen as discussed by Douglas Hofstadter in Gödel, Escher, Bach .
Since Huxley's time, there have been some more choices added to his epistemological menu. Two of my favorite are Nontheists and Ignostics. Nontheists profess no belief in god, which is importantly different, yet subtly so, from the atheistic belief in no god. Ignostics believe that any statements about god are nonsensical until the concept of god is better defined. Ignostics are fairly well aligned with theological noncognitivists who believe questions such as "Does God exist?" are meaningless.
Whatever your beliefs about god, perhaps the best, and certainly an honest, answer to give the curious child who asks, "Does God exist?" is "I don't know." Of course, as this essay has shown, the devil's in the details.
 T.H. Huxley, Collected Essays: Volume 5.
 Wikipedia entry for gnosis.
 Robert Nozick, Philosophical Explanations.
 Douglas Hofstadter, Gödel, Escher, Bach: an Eternal Golden Braid.