a person who offers views or theories on profound questions in ethics, metaphysics, logic, and other related fields.

a person who is deeply versed in philosophy.

a person who establishes the central ideas of some movement, cult, etc.

a person who regulates his or her life, actions, judgments, utterances, etc., by the light of philosophy or reason.

a person who is rationally or sensibly calm, esp. under trying circumstances.

Obsolete . an alchemist or occult scientist.

noun

logician , sage , savant , sophist , theorist , wise person , scholar , theorizer , thinker