I have spoken to many Christians about religion in my time: at beach mission, at Sunday school, at High School, at university and in day-to-day interactions. Until only quite recently, I had never heard any of them describe themselves as a theist. They never talked about theism. It was Christianity all the way.
In recent years, however, Christians seem to have introduced this new usage of “theism” wherein theism is cast as being directly opposed to atheism. While this is consistent with the original usage of the term – that is in opposition to emerging deism in the 1700s – it’s curious for a couple of reasons.
Firstly, the people who use the term “theist” do not consider themselves to be theists per se, they are Christian, or Jewish, or (potentially) Muslim or even some form of Hindu. Theism is a collective term which includes beliefs that the individual “theist” almost certainly holds to be untrue. Even a Universalist will hold the exclusivity of the individual faiths to be invalid. A Christian doesn’t believe “theism”, but rather Christianity.
Secondly, atheism does not have to oppose “theism”, not even strong atheism (or “new atheism”). Atheists are neither restricted nor inclined to address theism as a whole.
It is this latter point that I think is key. Creeping theism appears to be an attempt to defend an individual faith by hiding among other similar, but apparently false, faiths. The “one form of theism among many” argument goes a bit like this:
1. While you might have some legitimate argument against my form of theism, you can’t possibly prove every single form of theism to be false.
2. Therefore, it is possible that one form of theism is true.
3. Insert Plantinga's Ontological Argument here to prove that one form of theism is true (while hoping that no-one notices the logical fallacies involved).
4. If one form of theism is true, then it must be the best form of theism.
5. My form of theism is the best form of theism.
6. Therefore, my theism is true.
On the face of it, this doesn’t seem to make any difference since if you prove the theist’s individual form of theism to be false, then it’s false. However, this ignores the mental gymnastics of the average Christian. Say someone (an atheist or some alternate theist), knocks down a vital pillar of a Christian’s world view – for example by convincingly arguing that the errors and inconsistencies in the Bible show that the Bible is in error thus eliminating confidence in the prophesies foretelling the arrival of a messiah and indicating that the Gospels are likely to have been made up.
The Christian may be assailed by doubt, but she will not necessarily be crushed. She activates the “one form of theism among many” argument, noting that it is unlikely that the specific Biblical errors and inconsistencies raised will affect all forms of theism equally. Since there is no evidence which successfully addresses all forms of theism, there is therefore refuge in some hypothetical form(s) of theism. Naturally, the Christian believes that if any form of theism is true then it has to be hers. Not all forms of theism have been shown to be untrue and, therefore, her "best form of theism" must be true.
I know, it doesn’t make sense but the Greatest Living Christian Apologist regularly deploys equally weak and logically invalid arguments.
If anyone has any other theories regarding creeping theism, why the term "theism" has started to get so much traction in the Christian apologetics world, I’d be interested to hear them.