Just when we thought that terrorists could not become any more barbaric, this week in Sydney, Australia locals faithful to ISIS had planned public beheadings of random people off the street. Having recently returned from a visit to Australia I can attest that it is a wonderful place. Despite the high cost of living Australia boasts a vibrant democracy, a healthy economy, ample opportunities, a generous welfare system, lots of good weather, beautiful outdoors and people there seem happy and friendly. Yet we have also learned that one of the leaders of ISIS is Australian.

Who are these Australian (and British) ISIS members and what do they want? What would inspire Westerners to leave their comfortable homes and join a force that murders innocent people, including fellow citizens of their own countries, in the most barbaric fashion and then post videos of their dastardly acts on the internet to brag?

While watching the videos of Westerners dressed in thirteenth century clothing exhorting their “brothers back home” to join them in jihad it all suddenly made sense to me. While President Obama and other world leaders have called ISIS a cancer, I believe that ISIS can only truly be understood through the prism of religious fervor.

As a young man in my late teens and early twenties I too experienced the kind of religious passion and fervor that made me prepared to sacrifice everything to go out and convince fellow Jews to adopt my way of life. I was convinced that my way of doing Judaism was not only the best way, but for this generation it was positively the only way of being authentically Jewish. And because Jews were obligated by God to fulfill His commandments, it was my obligation to convince all Jews to follow suit. Somehow I was oblivious to the fact that my believing that something is correct, did not make it objectively so.

Believers often often mistake belief for empirical fact. When a passionate believer accepts that a certain book or person represents the word of God they begin to see that book or person as containing objective truth. They then cannot understand why others have been unable to perceive the truth as they see it. If the truth of God is so obvious, and is stated so clearly, they reason, why is it that others don’t realize it and are not following it? They conclude that it must be because the non-believers have not studied the right books, or have not met the right person, or maybe it is because their souls are tainted or they ate forbidden foods during childhood. The believer will rarely conclude that others do not share their beliefs simply because people are different and what appeals to the belief of one may not appeal to the other.

A wise person once compared faith to love. With love, you can introduce two people and either sparks begin to fly or they don’t. With love, we don’t all fall in love with the same person — what works for one, does not necessarily work for another. Love is also irrational.

Faith is similar. Reading the Koran, the Book of Mormon, the New Testament, The Torah etc. or listening to the talks of a religious figure won’t have the same impact on all people. Like love, not all people are going to find the same religious people, ideas or texts compelling. Like love, faith is not necessarily rational, the believer will often overlook innate human diversity and assume that the problem lies within the non-believer rather than with the religious book, teaching or teacher. They conclude therefore that they must force the issue somehow or that the “other” must be a lesser human, a heretic or an infidel.

ISIS is a combination of this sophomoric religious perspective and fervor paired with young testosterone-charged men carrying sophisticated weapons. But make no mistake about it, the religious bigotry that underlies this brutal and barbaric group of religious warriors is not exclusive to ISIS, it exists in every religion and often within political parties as well. If we want to overcome ISIS we need to also effectively address all forms of religious and political bigotry.

We need to make clear that belief, by its very nature, is not based on empirical evidence and it is therefore subjective. The fact that one person believes in Jesus, Moses, Mohammed or Joseph Smith as purveyors of the word of God does not make it objectively so. To me, my belief is real and I try and share with others why I have chosen to believe as I do as well as the value of following the Jewish way of life. But I have long ago given up the notion that my personal belief has objective value. This clear distinction between objective empiricism and belief which is by definition subjective needs to be the cornerstone of any religiously diverse and tolerant society. Without it we are left with shades of religious bigotry that in its extreme manifests in the form of ISIS and its public beheadings.

As our militaries and diplomats go about carrying out the extremely difficult task of destroying ISIS, we at home have our own work to do to combat religious and political bigotry wherever and whenever it rears its ugly head.