Sentence:  The great philosopher Thales of Miletus was a part-time <WSD>chrematist</WSD>. According to Aristotle, Thales was reproached with his personal poverty as clear evidence that his philosophy was of no use: 'Thales, if you're so smart, how come you ain't rich?" 
Meaning of the word marked with <WSD> tags:  One who studies or guides the wealth of the state; a political economist.