What does it mean to say that a court was wrong—and yet its ruling still governs?

Seminar 13 continues the Phronēsis Dilemma by turning from the general problem of practical error to a concrete sugya: the dispute between Rabban Gamliel and Rabbi Yehoshua in Rosh Hashanah 25.

The Ramban invokes this episode when discussing לא תסור and the competent dissenter who is convinced that Beis Din is mistaken. But the comparison raises a difficult problem. Kiddush HaChodesh has the exceptional rule of אתם — אפילו שוגגין, אפילו מזידין, אפילו מוטעין. And the sugya also invokes the principle of יפתח בדורו כשמואל בדורו.

So what exactly is being established at each stage?

This seminar develops three conceptual maps in order to separate questions that are easily collapsed:

What is the correct substantive judgment?

What makes a ...