Spiritual Beliefs: Wisdom or Idiocy?

A few years ago, during the bedraggled final tatters of our relationship, my ex-partner and I were out walking our dog when we got into yet another heated argument. I can’t even remember now what we were disagreeing about, but as he asserted his view I asked, ‘But how do you know that’s actually the case?’ 

He replied, angrily and brim-full of conviction: “I know that’s how it is, because I AM RIGHT!”