I read years ago that medieval rabbis (or perhaps earlier), when debating a point, would throw out anything when they had universal agreement and start over. They thought unanimity was too likely to be evidence of everyone jumping to a conclusion and following a fashion. I have never been able to locate a source for this, and it may not be true, but I have found it to be excellent, though not foolproof advice. Unanimous decisions are often rushed, not thought out, not waiting to see if different angles emerge. We recently had a church decision to call a new pastor that was overwhelming, but not unanimous. Unanimous would have worried me. It fairly screams "unrealistic expectations." There was a motion to report the vote as unanimous to the candidate. I had heard of such a thing when I was a Lutheran 40 years ago, and the explanation was that it was an expression of unity going forward. I believe it was moving some designated money from one purpose to another and the vote was 63-3 or something. Those who had voted against were now agreeing not to be passively, even unintentionally undermining the decision. The change was made and was reflected as a unanimous vote in the minutes, which struck me as weird, and not quite honest.
Unanimous decisions in department meetings or on psychiatric teams have gone bad for this reason, in my experience. They usually happen because there are one or more powerful figures that the others too easily agree with, or at least don't want to put in the energy to oppose. It is one of those Chestertonian paradoxes, that unanimity is often a sign of contention rather than unity, because of silent disagreement. Consider also the rigged elections of tyrants.
There is something similar that happens throughout the Bible. Knowledge of God and experience of God come from discussion. In a purely mechanistic Christianity, Jesus could have left a one-page document saying "Do this. Now I'm going to go die as an atonement for your sins, so you're good on that score," and then goodbye. He didn't do that. Wherever two or three are gathered. That's less than the minyan (10) required by Jews for morning prayers, but it's still not just one. There are councils and consultations right from the start, and these persist even in the very hierarchical Christian groups. Jesus chose twelve, not one. Notice that the prophets are not also rulers. The prophets bring a word, but it is for the elders, and ultimately the people, to work this out. I give an example of this from Rabbi Jonathan Sacks, writing about Wealth and Poverty over 30 years ago. Understanding Jewish Thought. Four rabbis give their opinion on "What is wealth?" and it is the interaction which is illuminating, rather than the comments of any one man.
(Sacks's full essay, which is excellent, is over at the Social Affairs Unit.)
Humorous diversion. It bothers me that I cannot remember where I read this, and have never seen it anywhere again. My guess is that it is from James Michener's The Source, which would be a reasonable but not authoritative reservoir of information about Medieval Jews. He did much research on everything he wrote, but cannot be relied on to see which were the main currents and which were backwaters. I had shared this observation about unanimity with a Jewish friend in the 1980's, who marveled "How do you know these things about my people that I, a Jew from New York, don't know?" (This had been a theme of our relationship, with me explaining to him why his Cohen uncles would not go into a cemetery or that the Jesus three-days-in-the-tomb was because of the Jewish reckoning, having died on a Friday afternoon - first day - and been hastily buried before Sabbath started. Saturday - Second day. Early Sunday morning - third day. "You know Judaism. What I know is Delancy Street," he would say.) I answered that I had always had many Jewish friends, being in AP classes, and after my renewal of Christian faith in 1975 I had also started reading a lot about Judaic roots. "I read Michener pretty soon after that."
He looked startled. "What did you read?"
"I don't know if that's the source, exactly. Torah would be the source."
It was my turn to look puzzled. We quickly worked out that he thought I had said Mishnah. "A gentile, interpreting oral law - I was impressed." He laughed. It was too bad I couldn't have kept up that image. Having read a popular novel is much less impressive.
If any of you can validate the story about medieval rabbis, or Talmudic teachers, and unanimity, I would be grateful.