In "The Lord of the Rings," there is “one ring to rule them all.” The “one ring” is the ultimate symbol of absolute power because it allows the ring’s possessor to control all other rings of power in fictional Middle-earth. There is no similar absolute “one rule to rule them all” in trial law in Texas, but there is a rule powerful enough to be called simply “the Rule.” Trial lawyers regularly invoke the Rule at the outset of a jury trial without further explanation. What is “the Rule” and why do judges and trial lawyers give it such a special place in the ordering of rules that it can be called simply the Rule?