Heraclitus is the first philosopher for whom there exists an extant written account of an enquiry into change. Writing in an aphoristic and esoteric style, Heraclitus remarked that, "On those stepping into rivers staying the same other and other waters flow". Or, more popularly: "One cannot step into the same river twice." This is generally taken to refer to the seeming contradiction between our calling the river "the same", while knowing that the material constituents of the river, the "waters", have completely changed. Simply put, :everything we wee is subject to change except change itself