"Twofold are the temptations to evade the burden of asking for the truth that matters. The one is the way of those who claim to have the truth and the other is the way of those who do not care for the truth. The first ones are called "the Jews" in our gospel. They point to their tradition which goes back to Abraham. Abraham is their father; so they have all truth, and do not need to be worried by the question which they encounter in Jesus. Many among us, Christians and secularists, are "Jews" in the sense of the Fourth Gospel. They point to their tradition which goes back to the Church Fathers, or to the popes, or to the Reformers, or to the makers of the American Constitution. Their church or their nation is their mother, so they have all truth and do not need to worry about the question of truth. Would Jesus tell them, perhaps, what He told the Jews—that even if the church or the nation is their mother, they carry with them the heritage of the father of untruth; that the truth they have is not the truth which makes free? Certainly there is no freedom where there is self-complacency about the truth of one’s own beliefs. There is no freedom where there is ignorant and fanatical rejection of foreign ideas and ways of life. There is not freedom but demonic bondage where one’s own truth is called the ultimate truth. For this is an attempt to be like God, an attempt which is made in the name of God."
"But those of us who dare to face the question of truth may listen to what the Fourth Gospel says about it. The first thing which strikes us is that the truth of which Jesus speaks is not a doctrine but a reality, namely, He Himself: "I am the truth." This is a profound transformation of the ordinary meaning of truth. For us, statements are true or false; people may have truth or not; but how can they be truth, even the truth? The truth of which the Fourth Gospel speaks is a true reality—that reality which does not deceive us if we accept it and live with it. If Jesus says, "I am the truth," he indicates that in Him the true, the genuine, the ultimate reality is present; or, in other words, that God is present, unveiled, undistorted, in His infinite depth, in His unapproachable mystery. Jesus is not the truth because His teachings are true. But His teachings are true because they express the truth which He Himself is. He is more than His words. And He is more than any word said about Him."
"The Church very early forgot the word of our Gospel that He is the truth; and claimed that her doctrines about Him are the truth. But these doctrines, however necessary and good they were, proved to be not the truth that liberates. Soon they became tools of suppression, of servitude under authorities; they became means to prevent the honest search for truth—weapons to split the souls of people between loyalty to the Church and sincerity to truth. And in this way they gave deadly weapons to those who attacked the Church and its doctrines in the name of truth. Not everybody feels this conflict. There are masses of people who feel safe under doctrinal laws. They are safe, but it is the safety of him who has not yet found his spiritual freedom, who has not yet found his true self. It is the dignity and the danger of Protestantism that it exposes its adherents to the insecurity of asking the question of truth for themselves and that it throws them into the freedom and responsibility of personal decisions, of the right to choose between the ways of the sceptics, and those who are orthodox, of the indifferent masses, and Him who is the truth that liberates. For this is the greatness of Protestantism: that it points beyond the teachings of Jesus and beyond the doctrines of the Church to the being of Him whose being is the truth."
"How do we reach this truth? "By doing it," is the answer of the Fourth Gospel. This does not mean being obedient to the commandments, accepting them and fulfilling them. Doing the truth means living out of the reality which is He who is the truth, making His being the being of ourselves and of our world. And again, we ask, "How can this happen?" "By remaining in Him" is the answer of the Fourth Gospel, i.e., by participating in His being. "Abide in me and I in you," he says. The truth which liberates is the truth in which we participate, which is a part of us and we a part of it. True discipleship is participation. If the real, the ultimate, the divine reality which is His being becomes our being we are in the truth that matters."
The whole book is available online here.