Conviction hits me badly (6)

I believe the answer is:
theism
'conviction' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'hits me badly' is the wordplay.
'badly' indicates anagramming the letters (letters in the wrong order).
'hits'+'me'='hitsme'
'hitsme' anagrammed gives 'THEISM'.
Can you help me to learn more?
(Other definitions for theism that I've seen before include "Belief in existence of a God revealed to man" , "Belief in a deity" , "of faith" , "Belief in a creator" , "The doctrine or belief in the existence of a God or gods" .)
