dogmatic

Short definition from Wiktionary

Adjective

1. 1
   Adhering only to principles which are true a priori, rather than truths based on evidence or deduction.
2. 2
   Pertaining to dogmas; doctrinal.
3. 3
   Asserting dogmas or beliefs in a superior or arrogant way; opinionated, dictatorial.

Noun

1. 1
   One of an ancient sect of physicians who went by general principles; opposed to the empiric.