Dr. Marquis teaches bioethics and ethical theory. His controversial essay on the ethics of abortion has been reprinted over 80 times and has been widely discussed. He has also written about issues in the ethics of medical research. His essay on the problems in the justification of the donation after cardiac death (DCD) protocol for vital organ transplantation was published in June 2010. In 2007-2008, Marquis was a visiting professor at Princeton University.