From The Kingdom of God is Within You by Leo Tolstoy.
Eighteen hundred years ago there appeared in the midst of the heathen Roman world a strange new doctrine, unlike any of the old religions, and attributed to a man, Christ.
This new doctrine was in both form and content absolutely new to the Jewish world in which it originated, and still more to the Roman world in which it was preached and diffused.
In the midst of the elaborate religious observances of judaism, in which, in the words of Isaiah, law was laid upon law, and in the midst of the Roman legal system worked out to the highest point of perfection, a new doctrine appeared, which denied not only every deity, and all fear and worship of them, but even all human institutions and all necessity for them. In place of all the rules of the old religions, this doctrine sets up only a type of inward perfection, truth, and love in the person of Christ, and—as a result of this inward perfection being attained by men—also the outward perfection foretold by the Prophets—the kingdom of God, when all men will cease to learn to make war, when all shall be taught of God and united in love, and the lion will lie down with the lamb. Instead of the threats of punishment which all the old laws of religions and governments alike laid down for non-fulfillment of their rules, instead of promises of rewards for fulfillment of them, this doctrine called men to it only because it was the truth.
No proof of this doctrine were offered except its truth, the correspondence of the doctrine with the truth. The whole teaching consisted in the recognition of truth and following it, in a greater and greater attainment of truth, and a closer and closer following of it in the acts of life. There are no acts in the doctrine which could justify a man and make him saved. There is only the image of truth to guide him, for inward perfection in the person of Christ, and for outward perfection in the establishment of the kingdom of God. The fulfillment of this teaching consists only in walking in the chosen way, in getting nearer to inward perfection in the imitation of Christ, and outward perfection in the establishment of the kingdom of God. The greater or less blessedness of a man depends, according to this doctrine, not on the degree of perfection to which he has attained, but on the greater or less swiftness with which he is pursuing it.