Theorist (noun)

1. A person who forms theories or conjectures about a subject without practical experience of it.
2. A person who provides theoretical explanation or analysis of a particular subject.

Origin:

Early 19th century: from french théoricien, from théorie (see theory).

Examples:

1. Einstein was a brilliant physicist and theoretical physicist.
2. Many of the theories developed by the political theorist have been proven to be accurate over time.
3. The sociologist is a well-known theorist in the field of urban studies.
4. The theorist's work has been widely accepted by scholars in the field of psychology.
5. The economist is regarded as one of the foremost economic theorists of the 20th century.