The notion that we humans are self equipped with instinctive qualities for ethical thinking is evidenced by our natural aversion to suffering for self and others. It seems to me that we are born with the former and that we develop the latter quite early in life through the most basic of natural experiences. Mencius’ illustration of our aversion to the suffering of a dog is a prime example of our natural sensitivity for the suffering of others. Our moment by moment quest for comfort seems to be a kinetic illustration of our natural discomfort in general.
It seems to me that such basic human qualities are the basis for ethical thinking, which in turn should translate to subsequent ethical behavior.