As ISIS slaughters its way though Syria and Iraq, it became inevitable that we’d hear from apologists who claim that ISIS is not in fact “true Islam,” and that its depredations are due to something other than religious motivation. Those motivations, say the apologists, are political (usually Western colonialism that engenders resentment), cultural (societal tradition), or anything other than religion.

These apologists, of course, which now include President Obama, are motivated by a desire to avoid criticizing religion at all costs—especially Islam. In America, criticizing religion is political suicide, and Obama naturally wants to do all he can to encourage “moderate” Muslims. As Sam Harris concluded on a post on his website, some “scholars and pseudo-scholars” cling to a ludicrous notion that the actions of jihadis like those of ISIS aren’t motivated by religion. As he noted: “experts claim that one can’t take Islamists and jihadists at their word: Their incessant declarations about God, paradise, martyrdom, and the evils of apostasy are nothing more than a mask concealing their real motivations.”

The apologists are also motivated by another form of denial. Yes, they say, jihadis may be motivated by Islam, but it’s not “true” Islam. True Islam is peaceful, and its adherents would never slaughter apostates, behead journalists, or forcibly convert non-Muslims. This is what Obama said the other night when explaining his plan to dismantle ISIS (or “ISIL,” as he calls it):

Now let’s make two things clear: ISIL is not Islamic. No religion condones the killing of innocents, and the vast majority of ISIL’s victims have been Muslim. … ISIL is a terrorist organization, pure and simple.

And here’s what he said in response to the beheading of journalist James Foley:

ISIL speaks for no religion … and no faith teaches people to massacre innocents. No just God would stand for what they did yesterday and what they do every single day.

Well, the beheading did happen, meaning either that God is not just, or there is no God—a possibility that Obama clearly can’t mention. (We’ll ignore for the moment that both the Qur’an and the Bible do indeed teach people to massacre innocents.)

The claims that ISIS is not a form of true Islam are often repeated by those who coddle religion. Here are Igor Volsky and Jack Jenkins of ThinkProgress explaining “Why ISIS is not, in fact, Islamic.” After quoting a verse from the Qur’an that seems to promote harmony among the world’s people, they note:

But ISIS clearly has little regard for this or other fundamental tenets of Islam. They have sparked the rage of Iraqi Muslims by carelessly blowing up copies of the Qur’an, and they have killed their fellow Muslims, be they Sunni or Shia. Even extremist Muslims who engage in warfare have strict rules of engagement and prohibitions against harming women and children, but ISIS has opted to ignore even this by slaughtering innocent youth and using rape and sexual slavery as a weapon.

They also quote Senator Rand Paul:

“I think it is important not only to the American public but for the world and the Islamic world to point out this is not a true form of Islam. This is an aberrant form that should not represent most of the civilized Islamic world.”

Volsky and Jenkins conclude, apparently by fiat, that ISIS is not a “true” faith: “No matter how many people they kill to gain power, how many fellow Muslims they terrorize into submission, or how loudly they scream their self-righteous blasphemy to the heavens, ISIS is not—nor will ever be—Islamic.”

Well, if ISIS is not Islamic, then the Inquisition was not Catholic. The fact is that there are no defensible criteria for whether a faith is “true,” since all faiths are man-made and accrete doctrine—said to come from God, but itself man-made—that becomes integral to those faiths. Whatever “true faith” means, it doesn’t mean “the right religion: the one whose God exists and whose doctrines are correct.” If that were so, we wouldn’t see Westerners trying to tell us what “true Islam” is.

No, if “true” means anything, it must mean “true to some principles.” As far as I can see, there are only two such principles: true to scripture or true to some code of conduct that the writer approves. But these definitions often contradict each other, so no “true” religion can be specified.

First, the truest religion could be that which sticks the closest to scripture. In that case the “truest” Christianity and Judaism would be literalist and fundamentalist. They would adhere to the creationism set out in Genesis, as well as to the immoral behaviors sanctioned by God in the Old Testament. These include killing those children who curse their parents, as well as adulterers and those who work on the Sabbath. Although these are clear moral dictates of God, no modern Christians or Jews obey them, for the rules are reprehensible. Nevertheless, there is a case to be made that a fundamentalist Southern Baptist is a “truer Christian” than a liberal Unitarian, and a misogynist Orthodox Jew a truer believer than a modern reform Jew.

You can cherry-pick the Qur’an as easily as you can the Bible, for both are filled with calls for violence and genocide that distress us. While Volksky and Jenkins quote one conciliatory verse from the Qur’an, there are a far greater number of verses calling for violence, characterizing Jews as “apes and swine,” dictating the killing of infidels and apostates, and dooming nonbelievers to hell. Why shouldn’t adherents to those views be considered “true” Muslims?

Actually, what people like Obama, Paul, Volsky, and Jenkins consider “true” faith is this: “faith that promotes the kind of behavior that I like.” So, as do all believers, the apologists pick and choose from scripture the dictates that they find congenial, ignoring the bad ones.

Many beliefs of some Muslim sects—like female genital mutilation and devaluating a woman’s testimony in court (according to sharia law, it’s worth only half of a man’s) —are not explicitly given in the Qur’an, the word of Allah supposedly dictated to Muhammad. Rather, they have become associated with Islam through the hadith and the sunnah (reported sayings, practices, and beliefs of Muhammad), or through simple tradition. ISIS has an extreme and fundamentalist interpretation of Muslim doctrine. But in exactly the same way, dogma about the immorality of abortion, homosexuality, premarital sex, and divorce have become part of Catholicism. They are theological interpretations of scripture that appeal to some people’s sense of morality. Others disagree. Whose faith is “truer”?

In the end, there is no “true” religion in the factual sense, for there is no good evidence supporting their claims to truth. Nor are there “true” religions in the moral sense. Every faith justifies itself and its practices by appeal to authority, revelation, and dogma. There are just some religions we like better than others because of their practical consequences. If that’s what we mean by “true,” we should just admit it. There’s no shame in that, for it’s certainly the case that societies based on some religions are more dysfunctional than others. Morality itself is neither objectively true nor false, but at bottom rests on subjective preferences: the “oughts” that come from what we see as the consequences of behaving one way versus another.

By all means let us say that ISIS is a strain of Islam that is barbaric and dysfunctional, but let us not hear any nonsense that it’s a “false religion.” ISIS, like all religious movements, is based on faith; and faith, which is belief in the absence of convincing evidence, isn’t true or false, but simply irrational.

A version of this post first appeared on WhyEvolutionIsTrue.