Final answer:
King appeals to a higher moral law by referencing St. Thomas Aquinas in his argument.
Step-by-step explanation:
King appeals to a higher moral law by referencing St. Thomas Aquinas in his argument. Aquinas was a theologian and philosopher who developed the concept of natural law, which suggests that there are universal moral principles that transcend man-made laws. By invoking Aquinas, King is emphasizing that the principles of nonviolence he advocates are rooted in a higher, moral authority.