Pope John Paul II’s homily at Edith Stein’s beatification mass gives us an excellent foundation for understanding her motivations:
Long before she realized it, she was caught by this fire” of the love of Christ. “At the beginning she devoted herself to freedom. For a long time Edith Stein was a seeker. Her mind never tired of searching and her heart always yearned for hope. She traveled the arduous path of philosophy with passionate enthusiasm. Eventually she was rewarded: she seized the truth. Or better: she was seized by it. Then she discovered that truth had a name: Jesus Christ. From that moment on, the incarnate Word was her One and All.”
She wrote in a letter to a fellow Carmelite nun; “Whoever seeks the truth is seeking God, whether consciously or unconsciously.” This quest would lead her to study the newly developing philosophical field of phenomenology which tries to explain the connection between the visible world and the world of ideas and values. It pushed back against the relativism and nihilism of modern philosophy. Working to show that objective truth existed and was within human reason’s grasp would pave the way for her eventual conversion to Catholicism.