agnostic vs agnostical

agnostic is a noun but agnostical is not a noun.

Word	Noun	Adjective	Verb	Adverb
agnostic	Yes	Yes	No	No
agnostical	No	Yes	No	No

As adjectives, agnostic and agnostical are synonyms defined as:

agnostic (noun)	agnostical (noun)
a person who claims that they cannot have true knowledge about the existence of God (but does not deny that God might exist)
someone who is doubtful or noncommittal about something

agnostic (adjective)	agnostical (adjective)
uncertain of all claims to knowledge	uncertain of all claims to knowledge
of or pertaining to an agnostic or agnosticism