"No proofs were given of [Jesus's] teaching, except the truth, except the correspondence of the teaching with the truth. The whole teaching consisted in the knowledge of the truth and in following it, in a greater and ever greater approximation to it, in matters of life. According to this teaching, there are no acts which can justify a man, make him righteous; there is only the model of truth which attracts all hearts, for the inner perfection — in the person of Christ, and for the outer — in the realization of the kingdom of God. The fulfillment of the teaching is only in the motion along a given path, in the approximation to perfection — the inner — the imitation of Christ, and the outer — the establishment of the kingdom of God."
Leo Tolstoy, The Kingdom of God is Within You