In this clip from the special "Soul-to-Soul" episode of "Super Soul Sunday," Oprah asks today's top spiritual experts to define the soul. "The soul is that part of you that existed before you were born and that will exist after you die," Gary Zukav says. "It's the highest, most noble part of you." Deepak Chopra says, "The soul is the core of your being." Tune in to "Super Soul Sunday" on OWN, Sundays at 11 a.m. ET.