Dig down to the root of just about any anti-religion statement and you’ll find at its foundation one of two philosophies: moral relativism or secular humanism. In modern American popular culture, these are the two belief systems that together comprise the intellectual roots of the anti-religion camp. These philosophies are in many ways hostile to each other, but their adherents are united against a common enemy. Both are seriously flawed. Both are in many ways religions themselves, and certainly among their adherents one finds those who are as insufferably self-righteous and dogmatic as any slick-haired televangelist.

Moral relativism is the belief that moral standards are grounded only in social custom, not in any universal or divine truth, so therefore all beliefs and moral standards are equally true. Sound familiar? It should, it’s the official religion of most university campuses and has spread throughout pop culture. “There ain’t no wrong, ain’t no right,” sang rock group Jane’s Addiction.

This belief is a little problematic. So the Aztec ritual of flinging virgins into live volcanoes is the moral equivalent of, say, Ghandi’s principles of non-violence? And yet, a religious person will often find himself on the business end of a moral relativist’s finger, wagged Church Lady-style in disapproval. The accompanying sermon is usually some version of “I’m superior because I’m so tolerant.”

The truth is that moral relativism invalidates itself. If every belief is equally true, that means I’m wrong for believing in a divine revelation as a universal criterion for human beliefs and actions. But of course, it also means that my religion is just as true as moral relativism. So there’s nothing for a moral relativist to feel superior about or disapprove of, even in reference to a member of the Manson Family.

Secular humanists, on the other hand, hold that only theirs is a valid belief system; namely, that belief in God (and all that follows from that) is wrong because His existence cannot be proved. And indeed it cannot be “proved” by some mathematical formula or scientific experiment; that’s why it’s called “faith.” Humans are left to derive His existence from His creation: a child’s smile, a Virginia autumn, a sunset. The believer finds it difficult to reflect on these marvels and consider them cosmic rolls of the dice.

In secular humanism, human reason is the ultimate criterion, the ultimate source of truth: “…dogmas, ideologies and traditions…must be weighed and tested by each individual and not simply accepted on faith,” states the Council for Secular Humanism. But this rather reasonable-sounding tenet is misleading, because to secular humanists, anyone who does accept a faith has not sufficiently “weighed and tested” it, since by definition it cannot be “proved” by the secular humanist criterion. This argument against religion fails because it assumes what it is trying to prove.

Secular humanists describe their belief system with neutral terms, calling it a “philosophy” or “conviction,” whereas they define religions with more loaded terms, as being “dogmas.” In reality, secular humanism and what would be traditionally considered “religions” like Islam and Christianity share a common ground in that they are all doctrines asserting an ultimate criterion of truth. Secular humanists simply dismiss belief in God out of hand because it’s not the ultimate source of truth that they believe in—the equivalent of a Christian trying to objectively prove that other religions are false because they don’t accept the Bible.

All belief systems, then, are not equally valid but they are all equally a set of assumptions whose validity must be judged on their own merits.