theorist

One who theorizes; a theoretician.

One who forms theories; one given to theory and speculation; a speculatist. It is often used with the implication of a lack of practical capacity.

One who forms theories; one given to theory and speculation; a speculatist.

someone who constructs theories, especially in the arts or sciences

an expert of some theory (v.)

someone who theorizes (especially in science or art)