The winning program was devised by a Canadian, Anatole Rapoport, and was called Tit-for-Tat. It was dazzlingly simple: it began by cooperating, and then repeated the last move of its opponent. It worked on the rule of “What you did to me, I will do to you,” or “measure for measure.” This was the first time scientific proof had been given for any moral principle.
What is fascinating about this chain of discoveries is that it precisely mirrors the central principle of the covenant G-d made with Noah: Whoever sheds the blood of man, by man shall his blood be shed; for in the image of G-d has G-d made man.
This is measure for measure (in Hebrew, middah k’neged middah), or retributive justice: as you do, so shall you be done to. In fact, at this point the Torah does something very subtle. The six words in which the principle is stated are a mirror image of one another: 1) Who sheds 2) the blood 3) of man, 3a) by man 2a) shall his blood 1a) be shed. This is a perfect example of style reflecting substance: what is done to us is a mirror image of what we do. The extraordinary fact is that the first moral principle set out in the Torah is also the first moral principle ever to be scientifically demonstrated. Tit-for-Tat is the computer equivalent of (retributive) justice: Whoever sheds the blood of man, by man shall his blood be shed.
The story has a sequel. In 1989, the Polish mathematician Martin Nowak produced a program that beats Tit-for-Tat. He called it Generous. It overcame one weakness of Tit-for-Tat, namely that when you meet a particularly nasty opponent, you get drawn into a potentially endless and destructive cycle of retaliation, which is bad for both sides. Generous avoided this by randomly but periodically forgetting the last move of its opponent, thus allowing the relationship to begin again. What Nowak had produced, in fact, was a computer simulation of forgiveness.
Once again, the connection with the story of Noah and the Flood is direct. After the Flood, G-d vowed: “I will never again curse the ground for man’s sake, although the imagination of man’s heart is evil from his youth; nor will I again destroy every living thing as I have done.” This is the principle of Divine forgiveness.
Thus the two great principles of the Noahide covenant are also the first two principles to have been established by computer simulation. There is an objective basis for morality after all. It rests on two key ideas: justice and forgiveness, or what the Sages called middat ha’din and middat rachamim. Without these, no group can survive in the long run.
In one of the first great works of Jewish philosophy – Sefer Emunot ve’Deot (The Book of Beliefs and Opinions) – Rabbi Saadia Gaon (882-942) explained that the truths of the Torah could be established by reason. Why then was revelation necessary? Because it takes humanity time to arrive at truth, and there are many slips and pitfalls along the way. It took more than a thousand years after Rabbi Saadia Gaon for humanity to demonstrate the fundamental moral truths that lie at the basis of G-d’s covenant with humankind: that co-operation is as necessary as competition, that co-operation depends on trust, that trust requires justice, and that justice itself is incomplete without forgiveness. Morality is not simply what we choose it to be. It is part of the basic fabric of the universe, revealed to us long ago by the universe’s Creator.
Adapted from “Covenant & Conversation,” a collection of Rabbi Jonathan Sacks’s parshiyot hashavua essays, published by Maggid Books, an imprint of Koren Publishers Jerusalem (www.korenpub.com), in conjunction with the Orthodox Union.
Rabbi Lord Jonathan Sacks, chief rabbi of the British Commonwealth since 1991, is the author of many books of Jewish thought, most recently “The Koren Sacks Rosh HaShana Mahzor” (Koren Publishers Jerusalem).