General Theorist:
* Teoryan (This is the most common and direct translation, but it's quite formal.)
* Mananaliksik (This means "researcher" and could be used for someone who develops theories.)
* Dalubhasa sa Teorya (This literally means "expert in theory" and emphasizes the specialized knowledge.)
Specific Types of Theorists:
* Teoryan sa Pulitika (Political theorist)
* Teoryan sa Ekonomiya (Economic theorist)
* Teoryan sa Sosyolohiya (Sociological theorist)
Other options:
* Tagapagpalagay (This means "proposer" and could be used for someone who develops a theory.)
* Tagapag-isip (This means "thinker" and could be used for someone who contemplates and develops ideas.)
The best translation will depend on the context and the specific type of theorist you're referring to.