If you’re an atheist who’s setting out to debate religious believers, there are three main categories of theism you can expect to meet. Although religious belief is one of the most diverse of human phenomena, with a limitless variety of gradations and exceptions, I think these three suffice to classify nearly all of the theists that a nonbeliever is likely to encounter. If you want to debate, it’s important to keep this in mind, because your strategy for dealing with each group needs to be different.
First of all, we have the fundamentalists. This is the most familiar group and the one that atheists encounter the most: the believers who interpret most of their holy book literally, who believe in miracles and demons and all the other trappings of supernaturalism, and a god who is anthropomorphic, judgmental, and intimately concerned with how humans lead their daily lives. The most zealously evangelistic, and the theocrats who most want their belief to be supported by the government, all fall into this category. Because they’re the loudest and the most organized, they also take a prominent role in political debates like access to abortion or teaching evolution in schools.
Second, we have the laypeople. These are the ordinary, mainstream believers who are by far the most numerous of the three groups. They usually attend church infrequently, viewing it as one obligation among others, and they participate in religious rituals mainly out of habit, or to maintain a sense of community. Their political beliefs span the spectrum. Members of this group can be frustratingly difficult for atheists to engage, because their views on the Bible (or whatever their church’s sacred text is) tend not to be variable so much as vague. Most of them have never read the Bible and know very little about what it says; for the most part, they believe without thinking much about it, and if asked to give a reason for their belief, few would be able to answer the question quickly or with confidence. Their notion of God tends to be somewhat less anthropomorphic than the fundamentalists, and certainly less demanding, less wrathful: more like a kindly grandparent than a stern tyrant.
Last, we have the theologians. These people, numerically the smallest of the three groups, are the elite, highly educated believers who are usually found among the clergy, the professional pundit class, and other rarefied circles. They tend to consider themselves more “sophisticated” than the other two groups, whose beliefs they view as simplistic and overly concrete, whereas they themselves tend to believe in a highly abstract, impersonal idea of God.
When debating with a fundamentalist, it’s essential to know your Bible. A fundamentalist’s identity is intimately bound up with their holy book, and an attack on it is an attack on them. The contradictions, scientific errors, textual alterations, and moral atrocities in religious texts make them unworthy of belief by any rational person, and that’s a point you should hammer on. Granted, there are well-rehearsed apologetics for most of these points, but the important thing is that you know them at all. As Dan Barker has said, they consider the Bible their weapon; atheists aren’t supposed to be using it against them. If you’re already familiar with it, you’ll have defanged their first and most common line of argument and will be able to very effectively put them on the defensive. A fundamentalist can’t let an attack on the Bible slide.
In my experience, the layperson will often claim that the bloody parts of the Bible represent corruption by misguided humans, and that God’s true message can be found in the better verses. The best way to respond to this is to ask, “So which verses in the Bible were written by God, and which were mistakenly added by people – and how do you tell the difference?” Point out that what they’re really doing is using their own conscience and sense of morality, and if they’re capable through conscience of telling good ideas apart from bad ones, then what do they need the Bible for in the first place – and why do they hold it in any special reverence? Lots of books contain both good and bad ideas, and many contain a much higher proportion of good ideas than the Bible.
For theologians, your strategy should be: Tie them to the Bible. Since most people in this group eschew literal, anthropomorphic interpretations of God, you should point out that the Bible teaches exactly such a view. It repeatedly speaks of God as getting angry, jealous, repentant, and possessing other human passions. It repeatedly speaks of God as intervening in the world and doing miracles – indeed, the essence of most major faiths, especially Christianity, is that they’re based on miracles. It repeatedly speaks of God demanding worship and punishing people who displease him. All these things are anathema to the theologian’s view, which carefully separates God from any point of contact with the world.
And since they’ll likely protest that the literal view is not their view, you can point out that it underlies their perspective, whatever they may think. Ask them if they pray, if they attend church, if they go to confession or otherwise participate in ritual, if they still use the language and participate in all the outward trappings of conventional religious belief – which most of them do – even though those activities make little sense except in the paradigm of the jealous, worship-demanding, miracle-working god they claim not to believe in.