Slavery is morally wrong. There is no doubt about this. Slavery is not immoral only “in some cases” or “in some circumstances.” Treating another human being as property is simply and unqualifiedly wrong. The New Testament advocates, or at least allows, slavery. So, the New Testament is morally wrong.

That’s a problem for Christianity. The only fallback position is “pick-and-choose-ism,” where one picks and chooses among the texts and doctrines to construct a personal version of the religion. (This strategy was mocked by conservative Catholics when they called their less-conservative brethren “cafeteria Catholics”—people who use birth control, believe in female clergy, don’t really believe in transubstantiation during Communion, but nevertheless consider themselves Catholics.) But if we allow pick-and-choose-ism, it undermines the claim that the Bible is true. If there are known false bits, then clearly it is not true that the whole thing is true, and then it seems far less likely that it is divinely inspired. And then, if you can’t tell which parts are divinely inspired and which are not, on what basis are you to pick and choose? At that point, you might as well just try to construct a good life without religion.

Or start the argument again: Slavery is wrong, so the New Testament is wrong, but that is the fault of its authors being “of their time” and not knowing a lot of what we know now. If that is the strategy, then we will have to update every part of the New Testament for the same reason. And we’ll be in the situation described above, not knowing what to pick and choose, and not having any good reason to stick with the claim that the New Testament is divinely inspired.

Slavery is not the only moral problem in the New Testament. There are other clear examples of things in that collection of documents that we cannot accept as morally correct: drowning a herd of pigs to get rid of someone’s mental illness (excuse me, demonic possession), stoning people, hate for LGBTQ people, shockingly rampant misogyny, and so on. There are some morally good bits, of course: love thy neighbor and turn the other cheek are nice ideas. Some of the best bits are not specifically Christian, though: the Golden Rule is found in cultures and religions all around the world before Christ.

The Old Testament fares no better, unsurprisingly. There are many examples in the Old Testament of moral claims we recognize as not just wrong but morally repugnant. Even the Ten Commandments are a moral mess.

Since the authors of the Bible didn’t know any science or medicine, it hardly makes sense to take them at their word about those things. There are well known mistakes about the age, origin, shape, constitution, and size of the universe in the Old Testament, which are not corrected in the New Testament. The story of the flood is a myth (literally: first invented in ancient Sumer and copied by authors of the Hebrew Bible). The OT even gets the development of life wrong, and it makes a foundational claim about an original pair of humans that is completely inconsistent with all the biological evidence.

Michael Ruse has argued that a Darwinian can be a Christian, but not a literalist about the Bible, since it takes metaphorical mental contortions to metaphorically reinterpret those Biblical passages about the first humans as referring to a spiritual rather than a factual claim. And then we are back to the interpretive problems pointed to above.

Here’s the kicker, though: The authors of the Bible had no more knowledge of supernatural matters than they had of natural things. They had no more evidence than we do, and a much poorer understanding of the world through which to interpret their experiences. So, their claims about supernatural things are doubtful, too, even if we do not have direct disproof of those claims. Again, we might as well just try to make a good life based on what we do know about the universe and forget about the impossible interpretive task of deciding which few bits of the Bible to retain and reinterpret to make them “true”.

Once we update the morality and science of the New Testament to be in line with what we know now, what is left that one could be confident enough to believe as a matter of religion? And what other beliefs need to be replaced that we have not yet realized need to be replaced in Christianity? The theological task here seems so difficult as to be absurd.

Why does this matter to me, a non-Christian? Why not just let Christians believe what they want? Because religious extremists are trying to impose their weird, false, and unfounded ideas on everyone. Making clear that religions like Christianity have no good claim to truth—nor to the moral high ground—helps to take some of the air out religious extremism and religious nationalism. Understanding this will, hopefully, embolden people to fight against this movement that aims to harm us.

No generation of humans, collectively, has ever had more or better knowledge about the world than we do now. In much of the world, we have never, individually, had more or easier access to the sum of human knowledge.

Sure, we might be slightly wrong about a few things in science, and there is plenty we do not yet know. It is possible (I’d say, likely) there are some things we will never be able to know. But in the list of things we know with high confidence, you’ll find astronomy, basic physics, chemistry, biology including evolution, big parts of medicine, and significant portions of psychology, social psychology, and other social sciences. Those are all areas where we have a great deal of knowledge with a very high degree of certainty.

We should act like we are at the pinnacle of human achievement, not like we are stuck in the Roman era. A lot has happened in the last 2000 years! We have immensely better moral and factual knowledge now. Let’s use it. Let’s make sure the Christian Nationalists do not get to impose their backwards views on the rest of us.