delusion

noun4

1. •
   An adamant belief in a falsehood despite incontestable evidence.
2. •
   That which is falsely or delusively believed or propagated; false belief; error in belief.

   • Hess, always a muddled man though not so doltish as Rosenberg, flew on his own to Britain under the delusion that he could arrange a peace settlement. — 1960
3. •
   A strong belief contrary to evidence.
4. •
   The state of being deluded or misled, or process of deluding somebody.

   • It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring.