1) Experimenter 2) John Locke, philosophically 3) Philosopher 
• (n.) An empiric.
(from the article `Empiricism`) When describing an everyday attitude, the word Empiricism sometimes conveys an unfavourable implication of ignorance of or indifference to relevant ...
Em·pir'i·cist noun An empiric. 
Someone who believes we are born tabula rasa, and become what we become as a result of experiences in our environment.
[n] - a philosopher who subscribes to empiricism
noun a philosopher who subscribes to empiricism