source: By Whoisjohngalt - Own work, CC BY-SA 4.0

a person who advocates a theory, proposal, or project:

｟かたく｠ 支持者; 提案者, 発議者

e.g. a collection of essays by both critics and proponents of graphology.

late 16th century: from Latin proponent- ‘putting forth’, from the verb proponere (see propound).