The term Cartesian refers to the work of the French philosopher and mathematician Rene Descartes. The crossword solutions for this term are ERGO (4 letters), RENE (4 letters), AXIS (4 letters), and SUM (3 letters). ERGO is a Latin word meaning 'THEREFORE' or 'CONSEQUENTLY'. RENE is the given name of Descartes. AXIS is a straight line about which a body or geometric object rotates. SUM is a mathematical term meaning the total of two or more numbers or quantities.