philosopher

n. one who philosophizes; one who studies the principles of existence behavior and knowledge

Philosophy is the discipline concerned with questions of how one should live (ethics); what sorts of things exist and what are their essential natures (metaphysics); what counts as genuine knowledge (epistemology); and what are the correct principles of reasoning (logic). The word itself is of Greek origin: φιλοσοφία (philosophía), a compound of φίλος (phílos: friend, or lover) and σοφία (sophía: wisdom).
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Noun
1. a specialist in philosophy
(hypernym) scholar, scholarly person, student
(hyponym) nativist
(classification) philosophy
2. a wise person who is calm and rational; someone who lives a life of reason with equanimity
(hypernym) person, individual, someone, somebody, mortal, human, soul

v. philosophize, think or reason like a philosopher, moralize

(n.)
One who reduces the principles of philosophy to practice in the conduct of life; one who lives according to the rules of practical wisdom; one who meets or regards all vicissitudes with calmness.
  

(n.)
One who philosophizes; one versed in, or devoted to, philosophy.
  

(n.)
An alchemist.