Truth is temporary, reality is temporary. There is no eternal knowledge and nothing that we believe in today could stay true forever. When an individual subscribes to a religion, a cult, a philosophy or any -ism they sacrifice their reason and hand over all control of their rational thinking. It is irrational to believe that truths which were handed over by mortals many centuries ago could still be true!
Indeed the very truths that underlie the reasoning above are shaky and temporary.