In this treatise I discuss not secularism, but the secularization of religion, which can attain a dimension where the polarity between holiness and secularization is transcended, and each one of us can attain oneness in our daily life. We who live in the first half of the 21st century must reflect on the beginning of religions in the contemporary world, and inquire into the meaning of original life from the standpoint of the experience that underlies all religions. In the 21st century we experience pluralism and complementarity, not only in the sphere of physics but also of religion, because each of us already understands that not only Christianity, but indeed all other religions-in which the self-awareness of each person is taken seriously as the central and most important issue-must go back to the beginning of all religions in the contemporary world and enquire into each of them from the standpoint of the experience of original life. The experience of original life or spirituality, which underlies all religions in this century, is originally one. Its representations (expressions) are very different from each other, because it is represented by the traditional culture of each nation, each of which has its own traditional and unique culture. In this sense I would like to inquire into the dimension transcending all dualities or polarities by comparing Christianity with Buddhism.